Ambient air pollution and preterm birth: A prospective birth cohort study in Wuhan, China

Association between ambient air pollution a week prior to delivery and preterm birth using a nationwide study in Sweden

BACKGROUND

Air pollution exposure has been linked with increased risk of preterm birth, which is one of the leading causes of infant mortality. Limited studies have attempted to explore these associations in low-polluted areas. In this study, we aimed to assess the association between short-term exposure to ambient air pollution and preterm birth in Sweden.

METHOD

In this population-based study we included preterm births between 2014 and 2019 from the Swedish Pregnancy Register. We applied a spatiotemporal model to estimate daily levels of particulate matter <2.5 μm (PM2.5), PM < 10 μm (PM10), nitrogen dioxide (NO2), and ozone (O3) at the residential address of each participant. We applied a time-stratified case-crossover design with conditional logistic regression analysis to estimate odds ratios (OR) of preterm birth per 10 μg/m3 (PM10, NO2, O3) and 5 μg/m3 (PM2.5) increase in air pollution exposure at 0-6-day lag. Two-pollutant models were applied to evaluate the independent association of each exposure on preterm birth. We also stratified by maternal characteristics to identify potential effect modifiers.

RESULTS

28,216 (4.5%) preterm births were included. An increase in O3 exposure was associated with increased odds of preterm birth [OR = 1.06 per 10 μg/m3 (95% CI, 1.02; 1.10]. PM2.5 and PM10 were not significantly associated with preterm birth, and NO2 displayed a negative nonlinear association with preterm birth. We did not observe any notable effect modification, but we found suggestive larger associations between O3 and preterm birth when stratifying by male sex, spontaneous delivery, and spring season.

CONCLUSIONS

Increased O3 exposure one week before delivery was associated with an increased risk of preterm birth in Sweden, a country with levels of air pollution below the current World Health Organization air quality guidelines. Increases in O3 levels with climate change make these findings especially concerning.

Preconception mitochondrial DNA copy number plays a crucial role in linking prenatal air pollution with the risk of preterm birth

The relationship between maternal peripheral blood mitochondrial DNA and adverse pregnancy outcomes, specifically preterm birth (PTB), remains uncertain. To investigate the effects of preconception mitochondrial DNA copy number (mtDNAcn) on the association between prenatal air pollutants exposure and PTB risk, a total of 1871 expectant mothers from six regions in Henan Province were recruited. Information regarding air pollutants was obtained from 151 environmental monitoring sites, and relative mtDNAcn was evaluated using real-time PCR analysis. After adjusting for potential confounding variables, it was determined that the risk of PTB increased with elevated levels of inhalable particulate matter (PM10), fine particulate matter (PM2.5), sulfur dioxide (SO2), carbon monoxide (CO) and ozone (O3) exposure (P < 0.05) but decreased with higher nitrogen dioxide (NO2) exposure (0.05 < P < 0.10) during the entire pregnancy. Additionally, the preconception relative mtDNAcn was lower in the PTB group (0.82 ± 0.23) compared to the term group (0.92 ± 0.29). Furthermore, for each 0.1-unit increase in preconception mtDNAcn, the risk of PTB decreased by 14.8%. Stratified analyses revealed that the risk of PTB rose with increasing O3 concentrations, regardless of the relative mtDNAcn. Moreover, the study found a significant association between PTB risk and prenatal exposure to elevated PM10, PM2.5, SO2, and CO, particularly in mothers with low mtDNAcn (≤0.88) (P < 0.05). Conversely, a decrease in the PTB risk was observed with elevated NO2 exposure in mothers with high mtDNAcn (>0.88). Interaction analysis revealed that exposure to PM10, PM2.5, SO2, NO2, and CO interacted with mtDNAcn, respectively, affecting PTB risk (P-interaction<0.05). These findings indicate a noteworthy association between PTB risk and prenatal air pollutants exposure, which is influenced by the preconception mtDNAcn.

Prenatal exposure to PM2.5 and childhood body mass index growth trajectories from birth to 6 years old

This study aimed to determine the relationships between prenatal PM2.5 exposure and childhood growth trajectories during the first 6 years of life. A total of 47,625 pairs of mothers and children were recruited from a prospective birth cohort conducted between 2011 and 2013 in Wuhan, China, and followed for 6 years. We used the group-based trajectory models to classify the population into three trajectory groups: slow growth (n = 13,671, 28.7%), normal growth (n = 29,736, 62.4%), and rapid growth (n = 4218, 8.9%). Multinomial logistic regression models were used to determine the associations of prenatal PM2.5 exposure and childhood growth trajectories. Compared to normal growth trajectory, increased PM2.5 exposure in trimester 1, trimester 2 and the entire pregnancy showed significant associations with an increased risk of the slow growth trajectory but reduced the risk for the rapid growth trajectory, significant association of prenatal PM2.5 exposure with rapid growth trajectory was only observed in the trimester 3. Stratified analyses displayed relatively stronger associations among those mothers with maternal age over 35 years, pre-pregnancy BMI ≥ 25 kg/m2, and previous delivery experience. Prenatal exposure to PM2.5, particularly during the midpoint period of pregnancy, was more likely to have a slow growth trajectory and a lower risk of rapid growth trajectory. Maternal age, pre-pregnancy BMI, and previous delivery experience might modify these associations.

Association between risk of preterm birth and long-term and short-term exposure to ambient carbon monoxide during pregnancy in chongqing, China: a study from 2016-2020

BACKGROUND

Preterm birth (PTB) is an important predictor of perinatal morbidity and mortality. Previous researches have reported a correlation between air pollution and an increased risk of preterm birth. However, the specific relationship between short-term and long-term exposure to carbon monoxide (CO) and preterm birth remains less explored.

METHODS

A population-based study was conducted among 515,498 pregnant women in Chongqing, China, to assess short-term and long-term effects of CO on preterm and very preterm births. Generalized additive models (GAM) were applied to evaluate short-term effects, and exposure-response correlation curves were plotted after adjusting for confounding factors. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using COX proportional hazard models to estimate the long-term effect.

RESULTS

The daily incidence of preterm and very preterm birth was 5.99% and 0.41%, respectively. A positive association between a 100 µg/m³ increase in CO and PTB was observed at lag 0-3 days and 12-21 days, with a maximum relative risk (RR) of 1.021(95%CI: 1.001-1.043). The exposure-response curves (lag 0 day) revealed a rapid increase in PTB due to CO. Regarding long-term exposure, positive associations were found between a 100 µg/m3 CO increase for each trimester(Model 2 for trimester 1: HR = 1.054, 95%CI: 1.048-1.060; Model 2 for trimester 2: HR = 1.066, 95%CI: 1.060-1.073; Model 2 for trimester 3: HR = 1.007, 95%CI: 1.001-1.013; Model 2 for entire pregnancy: HR = 1.080, 95%CI: 1.073-1.088) and higher HRs of very preterm birth. Multiplicative interactions between air pollution and CO on the risk of preterm and very preterm birth were detected (P- interaction<0.05).

CONCLUSIONS

Our findings suggest that short-term exposure to low levels of CO may have protective effects against preterm birth, while long-term exposure to low concentrations of CO may reduce the risk of both preterm and very preterm birth. Moreover, our study indicated that very preterm birth is more susceptible to the influence of long-term exposure to CO during pregnancy, with acute CO exposure exhibiting a greater impact on preterm birth. It is imperative for pregnant women to minimize exposure to ambient air pollutants.

Association Between Individual Air Pollution (PM10, PM2.5) Exposure and Adverse Pregnancy Outcomes in Korea: A Multicenter Prospective Cohort, Air Pollution on Pregnancy Outcome (APPO) Study

BACKGROUND

Prenatal exposure to ambient air pollution is linked to a higher risk of unfavorable pregnancy outcomes. However, the association between pregnancy complications and exposure to indoor air pollution remains unclear. The Air Pollution on Pregnancy Outcomes research is a hospital-based prospective cohort research created to look into the effects of aerodynamically exposed particulate matter (PM)10 and PM2.5 on pregnancy outcomes.

METHODS

This prospective multicenter observational cohort study was conducted from January 2021 to June 2023. A total of 662 women with singleton pregnancies enrolled in this study. An AirguardK® air sensor was installed inside the homes of the participants to measure the individual PM10 and PM2.5 levels in the living environment. The time-activity patterns and PM10 and PM2.5, determined as concentrations from the time-weighted average model, were applied to determine the anticipated exposure levels to air pollution of each pregnant woman. The relationship between air pollution exposure and pregnancy outcomes was assessed using logistic and linear regression analyses.

RESULTS

Exposure to elevated levels of PM10 throughout the first, second, and third trimesters as well as throughout pregnancy was strongly correlated with the risk of pregnancy problems according to multiple logistic regression models adjusted for variables. Except for in the third trimester of pregnancy, women exposed to high levels of PM2.5 had a high risk of pregnancy complications. During the second trimester and entire pregnancy, the risk of preterm birth (PTB) increased by 24% and 27%, respectively, for each 10 μg/m3 increase in PM10. Exposure to high PM10 levels during the second trimester increased the risk of gestational diabetes mellitus (GDM) by 30%. The risk of GDM increased by 15% for each 5 μg/m3 increase in PM2.5 during the second trimester and overall pregnancy, respectively. Exposure to high PM10 and PM2.5 during the first trimester of pregnancy increased the risk of delivering small for gestational age (SGA) infants by 96% and 26%, respectively.

CONCLUSION

Exposure to high concentrations of PM10 and PM2.5 is strongly correlated with the risk of adverse pregnancy outcomes. Exposure to high levels of PM10 and PM2.5 during the second trimester and entire pregnancy, respectively, significantly increased the risk of PTB and GDM. Exposure to high levels of PM10 and PM2.5 during the first trimester of pregnancy considerably increased the risk of having SGA infants. Our findings highlight the need to measure individual particulate levels during pregnancy and the importance of managing air quality in residential environment.

Associations between weekly gestational exposure of fine particulate matter, ozone, and nitrogen dioxide and preterm birth in a North Carolina Birth Cohort, 2003-2015

Background

Preterm birth (PTB; <37 weeks completed gestation) is associated with exposure to air pollution, though variability in association magnitude and direction across exposure windows exists. We evaluated associations between weekly gestational exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) with PTB in a North Carolina Birth Cohort from 2003 to 2015 (N = 1,367,517).

Methods

Daily average PM2.5 and daily 8-hour maximum NO2 concentration estimates were obtained from a hybrid ensemble model with a spatial resolution of 1 km2. Daily 8-hour maximum census tract-level concentration estimates for O3 were obtained from the EPA's Fused Air Quality Surface Using Downscaling model. Air pollutant concentrations were linked by census tract to residential address at delivery and averaged across each week of pregnancy. Modified Poisson regression models with robust errors were used to estimate risk differences (RD [95% confidence intervals (CI)]) for an interquartile range increase in pollutants per 10,000 births, adjusted for potential confounders.

Results

Associations were similar in magnitude across weeks. We observed positive associations for PM2.5 and O3 exposures, but generally null associations with NO2. RDs ranged from 15 (95% CI = 11, 18) to 32 (27, 37) per 10,000 births for PM2.5; from -7 (-14, -1) to 0 (-5, 4) for NO2; and from 4 (1, 7) to 13 (10, 16) for O3.

Conclusion

Our results show that increased PM2.5 exposure is associated with an increased risk of PTB across gestational weeks, and these associations persist in multipollutant models with NO2 and/or O3.

Relationship Between Outdoor Air Pollutant Exposure and Premature Delivery in China- Systematic Review and Meta-Analysis

Objective: Preterm birth (PTB) is considered as a public health problem and one of the main risk factors related to the global disease burden. The purpose of this study aims to explore the influence of exposure to major air pollutants at different pregnancies on PTB. Methods: The relationship between air pollutants and PTB in China was collected from cohort studies and case-control studies published before 30 April 2022. Meta-analysis was carried out with STATA 15.0 software. Results: A total of 2,115 papers were retrieved, of which 18 papers met the inclusion criteria. The comprehensive effect of pollutant exposure and PTB were calculated. PM2.5 during entire pregnancy and O3 exposure during third trimester were positively associated with preterm birth. Every 10 μg/m3 increase in the average concentration of PM2.5 during the whole pregnancy will increase the risk of premature delivery by 4%, and every 10 μg/m3 increase in the average concentration of O3 in the third trimester will increase the risk of premature delivery by 1%. Conclusion: Exposure to PM2.5 entire prenatal pregnancy and O3 in third trimester is associated with an increased risk of preterm birth occurrence.

Prenatal PM2.5 exposure increases the risk of adverse pregnancy outcomes: evidence from meta-analysis of cohort studies

Adverse pregnancy outcomes (APOs) are a significant cause of fetal death. A wide range of maternal psychological, social, and environmental factors may contribute to these outcomes. Mounting epidemiological studies have indicated that PM2.5 may result in these unfavorable consequences. Previously published meta-analyses have been updated and extended. Cohort studies were searched from three databases (up to July 24, 2023), and their quality was assessed by Newcastle-Ottawa Scale (NOS). Publication bias was examined by Egger's test and funnel plot. Despite a large number of studies showing similar results, the inconsistencies between these findings require careful generalization before concluding. This meta-analysis included 67 cohort studies from 20 countries, and the findings revealed that maternal PM2.5 exposure and five APOs were correlated significantly throughout pregnancy: preterm birth (PTB) (RR = 1.05; 95% CI: 1.03, 1.07); low birth weight (LBW) (RR = 1.02; 95% CI: 1.01, 1.04); small for gestational age (SGA) (RR = 1.03; 95% CI: 1.01, 1.04); stillbirth (RR = 1.24; 95% CI: 1.06, 1.45); and change in birthweight (weight change = -6.82 g; 95% CI: -11.39, -2.25). A positive association was found between APOs and PM2.5 exposure in this meta-analysis, and the degree of increased risk of APOs varied due to different gestation periods. Therefore, it is necessary to protect pregnant women at specific times.

Combined exposure to PM2.5 and PM10 in reductions of physiological development among preterm birth: a retrospective study from 2014 to 2017 in China

Background

Preterm birth (PTB) has been linked with ambient particulate matter (PM) exposure. However, data are limited between physiological development of PTB and PM exposure.

Methods

Trimester and season-specific PM exposure including PM2.5 and PM10 was collected from Jiaxing between January 2014 and December 2017. Information about parents and 3,054 PTB (gestational age < 37 weeks) outcomes such as weight (g), head circumference (cm), chest circumference (cm), height (cm) and Apgar 5 score were obtained from birth records. We used generalized linear models to assess the relationship between PTB physiological developmental indices and PM2.5, PM10 and their combined exposures. A binary logistic regression model was performed to assess the association between exposures and low birth weight (LBW, < 2,500 g).

Results

Results showed that there were 75.5% of low birth weight (LBW) infants in PTB. Decreased PM2.5 and PM10 levels were found in Jiaxing from 2014 to 2017, with a higher PM10 level than PM2.5 each year. During the entire pregnancy, the highest median concentration of PM2.5 and PM10 was in winter (61.65 ± 0.24 vs. 91.65 ± 0.29 μg/m3) followed by autumn, spring and summer, with statistical differences in trimester-specific stages. After adjusting for several potential factors, we found a 10 μg/m3 increase in joint exposure of PM2.5 and PM10 during the entire pregnancy associated with reduced 0.02 week (95%CI: -0.05, -0.01) in gestational age, 7.9 g (95%CI: -13.71, -2.28) in birth weight, 0.8 cm in height (95%CI: -0.16, -0.02), 0.05 cm (95%CI: -0.08, - 0.01) in head circumference, and 0.3 (95%CI: -0.04, -0.02) in Apgar 5 score, except for the chest circumference. Trimester-specific exposure of PM2.5 and PM10 sometimes showed an opposite effect on Additionally, PM2.5 (OR = 1.37, 95%CI: 1.11, 1.68) was correlated with LBW.

Conclusion

Findings in this study suggest a combined impact of fine particulate matter exposure on neonatal development, which adds to the current understanding of PTB risk and health.

Third trimester as the susceptibility window for maternal PM2.5 exposure and preterm birth: A nationwide surveillance-based association study in China

Maternal PM_2.5 exposure has been identified as a potential risk factor for preterm birth, yet the inconsistent findings on the susceptible exposure windows may be partially due to the influence of gaseous pollutants. This study aims to examine the association between PM_2.5 exposure and preterm birth during different susceptible exposure windows after adjusting for exposure to gaseous pollutants. We collected 2,294,188 records of singleton live births from 30 provinces of China from 2013 to 2019, and the gridded daily concentrations of air pollutants (including PM_2.5, O₃, NO₂, SO₂, and CO) were derived by using machine learning models for assessing individual exposure. We employed logistic regression to develop single-pollutant models (including PM_2.5 only) and co-pollutant models (including PM_2.5 and a gaseous pollutant) to estimate the odds ratio for preterm birth and its subtypes, with adjustment for maternal age, neonatal sex, parity, meteorological conditions, and other potential confounders. In the single-pollutant models, PM_2.5 exposure in each trimester was significantly associated with preterm birth, and the third trimester exposure showed a stronger association with very preterm birth than that with moderate to late preterm birth. The co-pollutant models revealed that preterm birth might be significantly associated only with maternal exposure to PM_2.5 in the third trimester, and not with exposure in the first or second trimester. The observed significant associations between preterm birth and maternal PM_2.5 exposure in the first and second trimesters in single-pollutant models might primarily be influenced by exposure to gaseous pollutants. Our study provides evidence that the third trimester may be the susceptible window for maternal PM_2.5 exposure and preterm birth. The association between PM_2.5 exposure and preterm birth could be influenced by gaseous pollutants, which should be taken into consideration when evaluating the impact of PM_2.5 exposure on maternal and fetal health.

Prenatal ambient air pollutants exposure and the risk of stillbirth in Wuhan, central of China

BACKGROUND

The existing studies on the relationships of prenatal ambient air pollutants exposure with stillbirth in the Chinese population are very limited and the results are inconsistent, and the susceptible windows and potential modifiers for air pollutants exposure on stillbirth remain unanswered.

OBJECTIVE

We aimed to determine the relationships between exposure to ambient air pollutants and stillbirth, and explored the susceptible windows and potential modifiers for air pollutants exposure on stillbirth.

METHODS

A population-based cohort was established through the Wuhan Maternal and Child Health Management Information System involving 509,057 mother-infant pairs in Wuhan from January 1, 2011 through September 30, 2017. Personal exposure concentrations of fine particles (PM_2.5), inhalable particles (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃) for mothers were estimated based on their residential address during pregnancy using the inverse distance weighted (IDW) method. We used the logistic regression models to determine the associations at different stages of pregnancy with adjustment for confounding factors.

RESULTS

There were 3218 stillbirths and 505,839 live births among the participants. For each 100 μg/m³ of CO and 10 μg/m³ of O₃ increase in the first trimester (conception to 13⁺⁶ weeks), the risk of stillbirth increased by 1.0% (OR = 1.01, 95%CI: 1.00-1.03) and 7.0% (OR = 1.07, 95%CI: 1.05-1.09). In the second trimester (14 weeks-27⁺⁶ weeks), PM_2.5, PM₁₀, CO, and O₃ exposure were closely related to the risk of stillbirth (P＜0.05). In the third trimester (28 weeks to delivery), for each 10 μg/m³ increase in exposure concentrations of PM_2.5, SO₂, and O₃, the risk of stillbirth increased by 3.4%, 5.9%, and 4.0%, respectively. O₃ exposure was positively relevant to the risk of stillbirth (OR = 1.11, 95%CI: 1.08-1.14) in the whole pregnancy. Exposure to NO₂ was not significantly associated with the risk of stillbirth. Stratified analyses also presented a stronger association among mothers with boy infant, living in rural areas, delivering between 2011 and 2013, and those without gestational hypertension and history of stillbirth.

CONCLUSION

This study provides evidence that maternal exposure to PM_2.5, PM₁₀, SO₂, CO, and O₃ were related to the increased risk of stillbirth. Both the second and third trimesters might be vital susceptible windows for stillbirth. Our findings expand the evidence base for the important impacts of air pollution on fetal growth.

Early Environment and Telomeres: a Long-Term Toxic Relationship

PURPOSE OF REVIEW

Telomere length (TL) shortening is a hallmark of biological aging. While studies have extensively focused on the impact of environmental exposures on TL in older populations, consistent evidence indicates that prenatal environmental exposures to air pollutants, polycyclic aromatic hydrocarbons, metals, and endocrine-disrupting chemicals influence TL shortening. Here, we summarize evidence linking prenatal environmental exposures with children's TL and discuss potential long-term effects.

RECENT FINDINGS

Current evidence shows that prenatal environmental exposures alter TL and identify pregnancy as a critical window of susceptibility for telomere damage in children. However, results vary across studies, possibly depending on the source, exposure time window, and stage evaluated. Additional research is needed to investigate whether early TL alterations mediate long-term health effects of offspring. Prenatal environmental exposures induce early childhood changes in TL. Based on known links between TL and biological aging, these alterations may have long-term impact on individuals' health throughout life.

The short-term effects of air pollution exposure on preterm births in Chongqing, China: 2015-2020

Accumulating evidence suggested that the risk of preterm births (PTBs) following prenatal exposure to air pollution was inconclusive. The aim of this study is to investigate the relationship between air pollution exposure in the days before delivery and PTB and assess the threshold effect of short-term prenatal exposure to air pollution on PTB. This study collected data including meteorological factors, air pollutants, and information in Birth Certificate System from 9 districts during 2015-2020 in Chongqing, China. Generalized additive models (GAMs) with the distributed lag non-linear models were conducted to assess the acute impact of air pollutants on the daily counts of PTB, after controlling for potential confounding factors. We observed that PM2.5 was related to increased occurrence of PTB on lag 0-3 and lag 10-21 days, with the strongest on the first day (RR = 1.017, 95%CI: 1.000-1.034) and then decreasing. The thresholds of PM2.5 for lag 1-7 and 1-30 days were 100 μg/m3 and 50 μg/m3, respectively. The lag effect of PM10 on PTB was very similar to that of PM2.5. In addition, the lagged and cumulative exposure of SO2 and NO2 was also associated with the increased risk of PTB. The lag relative risk and cumulative relative risk of CO exposure were the strongest, with a maximum RR at lag 0 (RR = 1.044, 95%CI: 1.018, 1.069). Importantly, the exposure-response curve of CO showed that RR increased rapidly when the concentration exceeded 1000 μg/m3. This study indicated significant associations between air pollution and PTB. The relative risk decreases with day lag, while the cumulative effect increases. Thus, pregnant women should understand the risk of air pollution and try to avoid high concentration exposure.

Ambient air pollution exposure and telomere length: a systematic review and meta-analysis

OBJECTIVE

This study aimed to provide evidence of the associations between pre- and post-birth and adulthood air pollution exposure with telomere length.

STUDY DESIGN

The databases of PubMed, Embase, and Web of Science were searched up to June 1st, 2022 in order to include relevant observational studies and perform a systematic review and meta-analysis.

METHODS

The random-effects meta-analysis was grouped by air pollutant and exposure window (pre- and post-birth and adulthood) to evaluate the summary effect estimate. Cochran's Q and I² statistics were used to evaluate the heterogeneity among the included studies. The quality of individual studies was evaluated using the national toxicology program/office of health assessment and translation risk of bias rating tool.

RESULTS

We identified 18 studies, covering 8506 children and 2263 adults from multiple countries. We found moderate evidence that particulate matter less than 2.5 μm (PM_2.5) exposure during the entire pregnancy (-0.043, 95% CI: -0.067, -0.018), nitrogen dioxide (NO₂) exposure during the first trimester (-0.016, 95% confidence interval [CI]: -0.027, -0.005), long-term adulthood PM_2.5 exposure were associated with shortening telomere length. Mild to high between-study heterogeneity was observed for the most tested air pollutant-telomere length combinations in different exposure windows.

CONCLUSIONS

This systematic review and meta-analysis provides the evidence which strongly supports that prenatal PM_2.5 and NO₂ exposures were related to reduced telomere length, while prenatal sulfur dioxide (SO₂) and carbon monoxide (CO) exposures, childhood PM_2.5, particulate matter less than 10 μm (PM₁₀), NO₂ exposures and short-term adulthood PM_2.5 and PM₁₀ exposures were not associated with telomere length. Further high-quality studies are needed to elaborate our suggestive associations.

Associations between short-term and long-term exposure to particulate matter and preterm birth

Despite the longstanding evidence on the effect of air pollutants on preterm birth (PTB), few studies have focused on its subtypes, including spontaneous preterm birth (sPTB) and medically indicated preterm birth (miPTB). Most studies evaluated only the short-term or long-term effects of particulate matter (PM) on PTB. Thus, we designed this study, based on a cohort of 179,385 women, to evaluate both short- and long-term effects of PM with diameters ≤2.5 μm and ≤10 μm (PM_2.5 and PM₁₀) on PTB, sPTB and miPTB in Shanghai. Generalized additive models (GAMs) were applied to evaluate short-term effects. Lagged effects were identified using different lag structures. Exposure-response correlation curves were plotted using GAMs after adjustment for confounders. ORs and 95% CIs were calculated using logistic regression to estimate the long-term effect after adjustment for confounders. There was 5.67%, 3.70% and 1.98% daily incidence of PTB, sPTB, and miPTB on average. Every 10 μg/m³ increase in PM_2.5 and PM₁₀ was positively associated with PTB and sPTB at lag 2 day. The exposure-response curves (lag 2 day) indicated a rapid increase in sPTB for PM_2.5 and a linear increase for PM₁₀, in PTB for PM_2.5 and PM₁₀ at concentrations over 100 μg/m³. Regarding long-term exposure, positive associations were found between 10 μg/m³ increases in PM_2.5 and PM₁₀ in 3rd trimester and greater odds of sPTB (aOR: 1.042, 95% CI: 1.018-1.065, and 1.018, 95% CI:1.002-1.034), and during the 3 months before conception and miPTB (aOR: 1.023, 95% CI: 1.003-1.042, and 1.017, 95% CI: 1.000-1.036). Acute exposure to PM_2.5 and PM₁₀ at lag 2 day and chronic exposure in 3rd trimester was significantly associated with sPTB, while miPTB was related to chronic exposure during the 3 months before pregnancy. These findings indicate that susceptibility windows of PM exposure can be influenced by different underlying etiologies of PTB.

Maternal atmospheric particulate matter exposure and risk of adverse pregnancy outcomes: A meta-analysis of cohort studies

Ambient air particulate exposure not only capable of elevating the risks of adverse pregnancy outcomes, but also has profound implications for human health, but the results are discrepant. This meta-analysis aimed to provide higher grade evidence on the impacts of air particulate on specific pregnancy outcomes. A total of 81 eligible cohort studies were included in this meta-analysis, of which the outcomes included preterm birth (PTB), moderate PTB, very PTB, extreme PTB, term low birth weight (TLBW), term birth weight (TBW), stillbirth (SB) and small for gestational age (SGA). The results showed that every 10 μg/m³ increase of PM_2.5 exposure associated with 2.7%-9.3% increase of PTB risk in entire pregnancy, 2nd and 3rd trimesters; 10.5%-19.3% increase of very PTB risk in entire pregnancy, 1st and 2nd trimesters; 8.3% and 10.1% increase of TLBW and SGA risk in entire pregnancy; 25.6% and 10.1% increase of SB in entire pregnancy and 3rd trimester; and -13.274 g and -4.916 g reduce of TBW during entire pregnancy and 2nd trimester, respectively. Every 10 μg/m³ increase of PM₁₀ exposure associated with 12.1% and 2.6% increase of PTB risk in entire pregnancy and 3rd trimester; 48.9% and 5.0% increase of moderate PTB risk in entire pregnancy and 2nd trimester; 14.4% and 10.3% increase of very PTB risk in 1st and 3rd trimesters; 2.9% increase of extremely PTB risk in 2nd trimester; 1.5%-3.8% and 2.9%-3.7% increase of TLBW and SGA risk in entire pregnancy, 1st and 2nd trimesters; 7.0% increase of SB risk in 3rd trimesters; and -4.537 g and -5.263 g reduce of TBW in 1st and 2nd trimesters, respectively. High mean annual PM concentrations were associated with more extreme adverse pregnancy outcomes (PTBs, SGA and SB), while low mean annual PM concentrations were associated with decreased TBW and increased risk of TLBW.

Impact of ambient air pollution exposure during pregnancy on adverse birth outcomes: generalized structural equation modeling approach

BACKGROUND

Air pollution and several prenatal factors, such as socio-demographic, behavioural, physical activity and clinical factors influence adverse birth outcomes. The study aimed to investigate the impact of ambient air pollution exposure during pregnancy adjusting prenatal risk factors on adverse birth outcomes among pregnant women in MACE birth cohort.

METHODS

Data for the study was obtained from the Mother and Child in the Environment (MACE) birth cohort study in Durban, South Africa from 2013 to 2017. Land use regression models were used to determine household level prenatal exposure to PM_2.5, SO₂ and NOx. Six hundred and fifty-six births of pregnant females were selected from public sector antenatal clinics in low socio-economic neighbourhoods. We employed a Generalised Structural Equation Model with a complementary log-log-link specification.

RESULTS

After adjustment for potential prenatal factors, the results indicated that exposure to PM_2.5 was found to have both significant direct and indirect effects on the risk of all adverse birth outcomes. Similarly, an increased level of maternal exposure to SO₂ during pregnancy was associated with an increased probability of being small for gestational age. Moreover, preterm birth act a mediating role in the relationship of exposure to PM_2.5, and SO₂ with low birthweight and SGA.

CONCLUSIONS

Prenatal exposure to PM_2.5 and SO₂ pollution adversely affected birth outcomes after controlling for other prenatal risk factors. This suggests that local government officials have a responsibility for better control of air pollution and health care providers need to advise pregnant females about the risks of air pollution during pregnancy.

Interactive effects of ambient air pollution and sunshine duration on the risk of intrahepatic cholestasis of pregnancy

INTRODUCTION

While the associations among ambient pollutants and various pregnancy complications are well documented, the effect of ambient pollutants on intrahepatic cholestasis of pregnancy (ICP) has not been examined. This study aimed to explore the effects of ambient pollutants and sunshine duration on ICP.

METHODS

The study enrolled 169,971 pregnant women who delivered between 2015 and 2020 in two hospitals. The associations between ICP and exposure to ambient pollutants and sunshine duration, averaged throughout different periods (including the 3 months before conception, 1st trimester and 2nd trimester), were estimated using a generalized linear model. The interaction effects of ambient pollutants and sunshine duration on ICP were estimated.

RESULTS

The fitted curves for ICP incidence were similar to the temporal trends of PM_2.5, PM₁₀, SO₂, CO and NO₂ but not that of O₃. The risk of ICP was significantly elevated following a 10-μg/m³ increase in PM_2.5 (aOR [adjusted odds ratio] = 1.057, 95% CI [confidence interval]: 1.017-1.099) and PM₁₀ (aOR = 1.043, 95% CI: 1.013-1.074) and a 1-h decrease in sunshine duration (aOR = 1.039, 95% CI: 1.011-1.068) during the 3 months before conception. In the second trimester, a 1-μg/m³ increase in the concentration of SO₂ was associated with an increased risk of ICP (aOR = 1.011, 95% CI: 1.001-1.021). Increased concentrations of PM_2.5 and PM₁₀ had interactive effects with reduced sunshine duration during the 3 months before conception on increasing the risk of ICP.

CONCLUSIONS

Exposure to PM_2.5 and PM₁₀ during the 3 months before conception and exposure to SO₂ in the second trimester were associated with an increased ICP risk. Reduced sunshine duration had an interactive effect with increased concentrations of PM_2.5 and PM₁₀ during the 3 months before conception on the occurrence of ICP.

Association between maternal family history of hypertension and preterm birth: modification by noise exposure and multivitamin intake

OBJECTIVE

To measure the effect of maternal family history of hypertension on preterm birth (PTB) and to identify factors that modified this association.

METHODS

A case-control study was nested in a prospective cohort of the entire pregnant population in Wuhan, China, from 2011 to 2013. Home-visit interviews were scheduled for all PTBs and their controls, to collect extensive information on maternal exposures to behavioral, environmental, and intergenerational risk factors of PTB. The effects of maternal family history of hypertension on PTB were measured by logistic regression analyses, controlling for potential confounders. Potential effect modifiers were examined using stratified analyses.

RESULTS

There were 2393 PTBs and 4263 full-term births out of all eligible births. A positive association was observed between maternal family history of hypertension and PTB, after adjusted for potential confounders (adjusted odds ratio: 1.17 [1.03, 1.33]). A higher effect was observed when mothers were exposed to certain noise during pregnancy (adjusted odds ratio: 1.37 [1.14, 1.65]) and/or when they did not take multivitamins during pregnancy (adjusted odds ratio: 1.46 [1.20, 1.78]), whereas, this association was weaker and no longer significant when mothers took multivitamins during pregnancy (adjusted odds ratio: 1.00 [0.84, 1.19]) and/or when they were not exposed to certain noise during pregnancy (adjusted odds ratio: 1.01 [0.85, 1.12]). The modification effect from maternal multivitamin intake was significant on both spontaneous and medically indicated PTBs, and the modification effect from maternal exposure to certain noise was only significant on spontaneous PTB.

CONCLUSIONS

Increased PTB risk was observed for pregnant women with a family history of hypertension in Wuhan, China. This effect was stronger when pregnant women did not take multivitamin and/or exposed to certain noise during pregnancy, than those who took multivitamin and/or unexposed to certain noise.

The causal and independent effect of ozone exposure during pregnancy on the risk of preterm birth: Evidence from northern China

The concentration of ozone (O₃) in the environment is gradually increasing, but there are limited reports on the exposure to O₃ during pregnancy on the risk of adverse birth outcomes. Our study aimed to examine the causal and independent effect of O₃ exposure during pregnancy on the risk of preterm birth (PTB) and to identify the critical window. Based on the baseline population of the birth cohort in Jinan, northern China, we obtained the individual exposure for each subject during pregnancy of ambient 8-h moving average O₃ through the inverse distance weighting model. The effect of O₃ exposure during pregnancy on PTB was evaluated through the time-dependent Cox proportional-hazard models. And we assessed the causal relationship by controlling unknown confounding factors using the instrumental variable (IV) analysis, estimated the independent effect by principal component analysis, and identified the critical window period of exposure through the distributed lag model. Among 6501 subjects, 285 mothers delivered prematurely. The median (IQR) of O₃ concentration during pregnancy was 109.51 (23.54) μg/m³. The high level of O₃ exposure (>173.64 μg/m³) increased the risk of PTB, with HR of 1.92 (95% CI: 1.38-2.66). Furthermore, the HR (95% CI) of the O₃ estimated value calculated by the IV (wind speed) on the risk of PTB was 2.63 (1.41-4.88). In addition, the high level of O₃ exposure was associated with the risk of PTB in the 13th-18th gestational weeks. Therefore, the high level of O₃ exposure during pregnancy may independently increase the risk of PTB, which may be a causal effect. The 13th to 18th week of gestation is a critical window for preventing this risk.

Health effects of exposure to sulfur dioxide, nitrogen dioxide, ozone, and carbon monoxide between 1980 and 2019: A systematic review and meta-analysis

The burden of disease attributed to the indoor exposure to sulfur dioxide (SO₂ ), nitrogen dioxide (NO₂ ), ozone (O₃ ), and carbon monoxide (CO) is not clear, and the quantitative concentration-response relationship is a prerequisite. This is a systematic review to summarize the quantitative concentration-response relationships by screening and analyzing the polled effects of population-based epidemiological studies. After collecting literature published between 1980 and 2019, a total of 19 health outcomes in 101 studies with 182 health risk estimates were recruited. By meta-analysis, the leave-one-out sensitivity analysis and Egger's test for publication bias, the robust and reliable effects were found for SO₂ (per 10 μg/m³ ) with chronic obstructive pulmonary diseases (COPD) (pooled relative risks [RRs] 1.016, 95% CI: 1.012-1.021) and cardiovascular diseases (CVD) (RR 1.012, 95%CI: 007-1.018), respectively. NO₂ (per 10 μg/m³ ) had the pooled RRs for childhood asthma, preterm birth, lung cancer, diabetes, and COPD by 1.134 (1.084-1.186), 1.079 (1.007-1.157), 1.055 (1.010-1.101), 1.019 (1.009-1.029), and 1.016 (1.012-1.120), respectively. CO (per 1 mg/m³ ) was significantly associated with Parkinson's disease (RR 1.574, 95% CI: 1.069-2.317) and CVD (RR 1.024, 95% CI: 1.011-1.038). No robust effects were observed for O₃ . This study provided evidence and basis for further estimation of the health burden attributable to the four gaseous pollutants.

Machine learning-based risk factor analysis of adverse birth outcomes in very low birth weight infants

This study aimed to analyze major predictors of adverse birth outcomes in very low birth weight (VLBW) infants including particulate matter concentration (PM₁₀), using machine learning and the national prospective cohort. Data consisted of 10,423 VLBW infants from the Korean Neonatal Network database during January 2013-December 2017. Five adverse birth outcomes were considered as the dependent variables, i.e., gestational age less than 28 weeks, gestational age less than 26 weeks, birth weight less than 1000 g, birth weight less than 750 g and small-for-gestational age. Thirty-three predictors were included and the artificial neural network, the decision tree, the logistic regression, the Naïve Bayes, the random forest and the support vector machine were used for predicting the dependent variables. Among the six prediction models, the random forest had the best performance (accuracy 0.79, area under the receiver-operating-characteristic curve 0.72). According to the random forest variable importance, major predictors of adverse birth outcomes were maternal age (0.2131), birth-month (0.0767), PM₁₀ month (0.0656), sex (0.0428), number of fetuses (0.0424), primipara (0.0395), maternal education (0.0352), pregnancy-induced hypertension (0.0347), chorioamnionitis (0.0336) and antenatal steroid (0.0318). In conclusion, adverse birth outcomes had strong associations with PM₁₀ month as well as maternal and fetal factors.

Relationship between ambient air pollution and preterm birth: a retrospective birth cohort study in Yan'an, China

Preterm birth (PTB) has been associated with exposure to air pollution, but it is unclear whether effects might vary among air pollution sources in a valley city, and yet few studies have investigated refined susceptible windows for PTB. We performed a retrospective birth cohort study in Yan'an city, a typical valley city in the west of China, and analyze the effects of air pollutants on premature delivery, identify critical windows for maternal air pollutants exposure and PTB. The pregnant women who gave birth in the Affiliated Hospital of Yan'an University and Yan'an people's Hospital from January 1, 2018 to December 31, 2019 were selected as the research objects. A questionnaire survey and medical records were conducted. The daily average concentrations of particulate matter with aerodynamic diameters of ≤ 2.5 μm (PM_2.5) and ≤ 10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂) and ozone (O₃) in Yan'an City from January 1, 2017 to December 31, 2019 were collected. After controlling the confounding factors of PTB by logistic regression model, the effect of air pollutants on preterm birth was analyzed. After controlling the confounding factors such as maternal age, gestational times and gestational hypertension syndrome, PTB was associated with exposure to third trimester PM₁₀ (adjusted odds ratio [aOR] = 1.019, 95% confidence interval [95%CI] = 1.004-1.035). PTB risk increased with second trimester exposure to SO₂ (aOR = 1.039, CI = 1.011-1.068), also with third trimester (aOR = 1.031, CI = 1.010-1.053). PTB was also associated with third trimester O₃ (aOR = 1.023, CI = 1.005-1.041). This study indicates that maternal exposure to PM₁₀, SO₂ and O₃ might lead to increased risk of PTB, and critical exposure windows were inconsistent.

First Trimester of Pregnancy as the Sensitive Period for the Association between Prenatal Mosquito Coil Smoke Exposure and Preterm Birth

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother-child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05-1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09-1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03-1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01-1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.

The type of previous abortion modifies the association between air pollution and the risk of preterm birth

BACKGROUND

Air pollution and previous abortion have been reported to be related to preterm birth (PTB). But rare study examined the effect of air pollution on PTB risk among mothers with previous abortion.

OBJECTIVE

To estimate the effect of air pollution on PTB and the potential effect modification of previous abortion on such an association in rural part of Henan province (China).

METHOD

Based on National Free Preconception Health Examination Project (NFPHEP), information from the medical records of 57,337 mothers with previous abortion were obtained. An inverse distance-weighted model was used to estimate exposure levels of air pollutants. The effect of air pollution on the risk of PTB was estimated with a multiple logistic regression model. Stratified and interaction analyses were undertaken to explore the potential effect modification of previous abortion on this association.

RESULTS

The risk of PTB was positively associated with exposure to levels of nitrogen dioxide (NO₂; OR: 1.03; 95%CI: 1.02-1.04)], and sulfur dioxide (SO₂; 1.04; 1.02-1.07), and negatively associated with ozone (O₃) exposure (0.97; 0.97-0.98) during the entire pregnancy. Besides, we observed a positive effect of carbon monoxide (CO) exposure during the third trimester of pregnancy on PTB (1.14; 1.01-1.29). The type of previous abortion could modify the effect of air pollution on the PTB risk (P-_interaction < 0.05). Compared with mothers with previous induced abortion, mothers with previous spontaneous abortion carried a higher risk of PTB induced by NO₂, CO, and O₃.

CONCLUSIONS

The risk of PTB was positively associated with levels of NO₂, SO₂ and CO, and negatively associated with the O₃ level. The types of previous abortion could modify the effect of air pollution on PTB. Mothers who had an abortion previously, especially spontaneous abortion, should avoid exposure to air pollution to improve their pregnancy outcome.

Assessing the effect of fine particulate matter on adverse birth outcomes in Huai River Basin, Henan, China, 2013-2018

Previous studies have indicated that maternal exposure to particles with aerodynamic diameter <2.5 μm (PM_2.5) is associated with adverse birth outcomes. However, the critical exposure windows remain inconsistent. A retrospective cohort study was conducted in Huai River Basin, Henan, China during 2013-2018. Daily PM_2.5 concentration was collected using Chinese Air Quality Reanalysis datasets. We calculated exposures for each participant based on the residential address during pregnancy. Binary logistic regression was used to examine the trimester-specific association of PM_2.5 exposure with preterm birth (PTB), low birth weight (LBW) and term LBW (tLBW), and we further estimated monthly and weekly association using distributed lag models. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for each 10 μg/m³ increase in PM_2.5 exposure. Stratified analyses were performed by maternal age, infant gender, parity, and socioeconomic status (SES). In total, 196,780 eligible births were identified, including 4257 (2.2%) PTBs, 3483 (1.8%) LBWs and 1770 (0.9%) tLBWs. Maternal PM_2.5 exposure during the second trimester were associated with the risk of PTB and LBW. At the monthly level, the PTB and LBW risks were associated with PM_2.5 exposure mainly in the 4th -6th month. By estimating the weekly-specific association, we observed that critical exposure windows of PM_2.5 exposure and PTB were in the 18th- 27th gestational weeks. Stronger associations were found in younger, multiparous mothers and those with a female baby and in low SES. In conclusion, the results indicate that maternal PM_2.5 exposure during the second trimester was associated with PTB and LBW. Younger, multiparous mothers and those with female babies and in low SES were susceptible.

Exposure to Ambient Air Pollutant PM10 in the Second Trimester of Pregnancy Is Associated with Preterm Birth: A Birth-Based Health Information Cohort Study

Objectives

We evaluated the effects of exposure to high concentrations of particulate matter (PM)10 on preterm birth (PTB) and identified a critical concentration of PM10 that could lead to PTB via a birth-based health information cohort study.

Methods

We conducted a birth-based cohort study consisting of nonanomalous singleton births at 22-42 weeks. PTB was defined as babies born alive before 37 weeks of pregnancy. Pregnancy period exposure averages were estimated for PM10 based on the China National Environmental Monitoring Centre (CNEMC). Pregnant women who lived within 50 km of the monitor station were recruited into this study. Logistic regression analyses were performed to determine the association between PTB and exposure to PM10 at different pregnancy periods with adjustment for confounding factors.

Results

The relative frequency of PTB was 8.7% in the study cohort of 5,291 singleton live births. A total of 1137 women had a high level of PM10 exposure (≥60 μg/m3) in the second trimester of pregnancy. The average concentrations of PM10 in the first, second, and third trimesters of pregnancy and throughout pregnancy were 53.8 μg/m3, 54.2 μg/m3, 55.6 μg/m3, and 54.3 μg/m3, respectively. The generalized additive model (GAM) analysis showed that there was a nonlinear correlation between PM10 and PTB in the second trimester of pregnancy (P < 0.001). The adjusted odds ratio between PTB and low concentration PM10 exposure (PM10 < 60 μg/m3) in the second trimester of pregnancy was 1.01 (95% CI 0.95-1.05). However, high PM10 exposure (PM10 ≥ 60 μg/m3) in the second trimester of pregnancy had an increased PTB risk even after adjustment for coexisting risk factors with an adjusted odds ratio of 1.78 (95% CI 1.69-1.87), and the incidence of PTB increased with an increase in PM10 exposure.

Conclusions

Our research discovered that exposure to high levels of PM10 increases the risk of PTB and the second trimester is the most vulnerable gestational period to ambient air pollution exposure. PM10 concentrations more than 60 μg/m3 are detrimental to pregnant women in their second trimester. This study has implications for health informatics-oriented healthcare decision support systems.

Effects of physical activity intensity on adulthood obesity as a function of long-term exposure to ambient PM2.5: Observations from a Chinese nationwide representative sample

Long-term exposure to PM_2.5 has been associated with increased obesity risk, while physical activity (PA) is a suggested protective factor. This raises a dilemma whether the increased dose of PM_2.5 due to PA-intensified ventilation would offset the benefits of PA. Using a national representative sample, we aim to (1) ascertain inclusive findings of the association between PA and obesity, and (2) examine whether PM_2.5 exposure modifies the PA-obesity relationship. We recruited 91,121 Chinese adults from 31 provinces using a multi-stage stratified-clustering random sampling method. PM_2.5 was estimated using a validated machine learning method with a spatial resolution of 0.1° × 0.1°. PA intensity was calculated as metabolic equivalent (MET)-hour/week by summing all activities. Body weight, height, and waist circumference (WC) were measured after overnight fasting. Obesity-related traits included continuous outcomes (Body mass index [BMI], WC, and waist-to-height ratio (WHtR)) and binomial outcomes (general obesity, abdominal obesity, and WHtR obesity). Generalized linear regression models were used to estimate the interaction effects between PM_2.5 and PA on obesity, controlling for covariates. The results indicated that each IQR increase in PA was associated with 0.078 (95% CI: -0.096 to -0.061) kg/m², 0.342 (-0.389 to -0.294) cm, and 0.0022 (-0.0025 to -0.0019) decrease in BMI, WC, and WHtR, respectively. The joint association showed that benefits of PA on obesity were attenuated as PM_2.5 increased. Risk of abdominal obesity decreased 11.3% (OR = 0.887, 95% CI: 0.866, 0.908) per IQR increase in PA among the low-PM_2.5 (≤55.9 μg/m³) exposure group, but only 5.5% (OR = 0.945, 95% CI: 0.930, 0.960) among the high-PM_2.5 (>55.9 μg/m³) exposure group. We concluded the increase in PA intensity was significantly associated with lower risk of obesity in adults living across mainland China, where annual level of PM_2.5 were mostly exceeding the standard. Reducing PM_2.5 exposure would enhance the PA benefits as a risk reduction strategy.

Associations of maternal exposure to fine particulate matter with preterm and early-term birth in high-risk pregnant women

Background

Environmental pollution is a risk factor for adverse birth outcomes, especially preterm birth (PTB) and early-term birth (ETB). It has been revealed that exposure to fine particulate matter (PM_2.5) during pregnancy increase the prevalence of PTB. However, the relationship between PM_2.5 exposure and ETB has not been elucidated. In high-risk pregnancies, whether PM_2.5 exposure will bring higher risk of PTB and ETB than in normal pregnancies is still unclear, and the susceptible exposure window is obscure. Therefore, it is worthy of assessing the risk on PTB and ETB and identifying the susceptible exposure windows of PM_2.5 exposure in high-risk pregnant women.

Results

This paper collected the clinical data of 7974 singletons, high-risk pregnant women in Peking University First Hospital from 2014 to 2018, and analyzed them using logistic regression and stratified analysis. We observed that exposure to high-level (≥ 75 µg/m³) of PM_2.5 during the third trimester of pregnancy increases the risk of PTB and ETB (PTB: odds ratio[OR] = 1.43, 95% confidence interval [CI]:1.05–1.93. ETB: OR = 1.29, 95%CI: 1.09–1.54). Furthermore, the effects of each 10ug/m³ increase in PM_2.5 on PTB and ETB were significant during the third trimester (PTB: OR = 1.35, 95%CI:1.16–1.58. ETB: OR = 1.12, 95%CI:1.02–1.22) and the entire pregnancy (PTB: OR = 6.12, 95%CI:4.27–8.89. ETB: OR = 1.96, 95%CI:1.59–2.43) in the high-level exposure group.

Conclusions

These results suggest that high-level PM_2.5 exposure during pregnancy is associated with high risk of PTB and ETB in high-risk pregnancies. The third trimester of pregnancy is speculated to be the susceptible exposure window.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41021-022-00239-0.

Residential proximity to greenness and adverse birth outcomes in urban areas: Findings from a national Canadian population-based study

BACKGROUND

Over the last decade, several studies have reported that residential proximity to vegetation, or 'greenness', is associated with improved birth outcomes, including for term birth weight (TBW), preterm birth (PTB), and small for gestational age (SGA). However, there remain several uncertainties about these possible benefits including the role of air pollution, and the extent to they are influenced socioeconomic status.

METHODS

We addressed these gaps using a national population-based study of 2.2 million singleton live births in Canadian metropolitan areas between 1999 and 2008. Exposures to greenness, fine particulate matter (PM_2.5), and nitrogen dioxide (NO₂) were assigned to infants using the postal code of their mother's residence at the time of birth. The Normalized Difference Vegetation Index (NDVI) was used to characterize greenness, while estimates of ambient PM_2.5 and NO₂ were estimated using remote sensing, and a national land-use regression surface, respectively. Multivariable regression analysis was performed to describe associations between residential greenness and the birth outcomes. Stratified analyses explored whether these associations were modified by neighbourhood measures of socioeconomic status.

RESULTS

Mothers who lived in greener areas had a lower risk of low TBW, PTB, and SGA babies. These associations persisted after adjustment for ambient NO₂ and PM_2.5. Specifically, in fully adjusted models, an interquartile range (IQR = 0.16) increase in the NDVI within a residential buffer of 250 m yielded odds ratios of 0.93 (95% confidence interval (CI): 0.92, 0.94), 0.94 (95% CI: 0.92, 0.95), and 0.94 (95% CI: 0.93, 0.95) for the outcomes of PTB, low TBW, and SGA, respectively. Similarly, an IQR increase in greenness was associated with a 16.3 g (95% CI: 15.3, 17.4) increase in TBW. We found inverse associations between greenness and the occurrence of adverse birth outcomes regardless of the socioeconomic status of the neighbourhood.

INTERPRETATION

Our findings support the hypothesis that residential greenness contributes to healthier pregnancies, that these associations are independent from exposure to air pollution. , and that proximity to greenness benefits all mothers regardless of socioeconomic status.

Association between Maternal Exposure to Ambient Air Pollution and the Risk of Preterm Birth: A Birth Cohort Study in Chongqing, China, 2015-2020

Recent study results on the association between maternal exposure to ambient air pollution with preterm birth have been inconsistent. The sensitive window of exposure and influence level of air pollutants varied greatly. We aimed to explore the association between maternal exposure to ambient air pollutants and the risk of preterm birth, and to estimate the sensitive exposure time window. A total of 572,116 mother–newborn pairs, daily concentrations of air pollutants from nearest monitoring stations were used to estimate exposures for each participant during 2015–2020 in Chongqing, China. We applied a generalized additive model and estimated RRs and 95% CIs for preterm birth in each trimester and the entire pregnancy period. In the single-pollutant model, we observed that each 10 μg/m³ increase in PM_2.5 had a statistically significant effect on the third trimester and entire pregnancy, with RR = 1.036 (95% CI: 1.021, 1.051) and RR = 1.101 (95% CI: 1.075, 1.128), respectively. Similarly, for each 10 μg/m³ increase in PM₁₀, there were 2.7% (RR = 1.027, 95% CI: 1.016, 1.038) increase for PTB on the third trimester, and 3.8% (RR = 1.038, 95% CI: 1.020, 1.057) increase during the whole pregnancy. We found that for each 10 mg/m³ CO increases, the relative risk of PTB increased on the first trimester (RR = 1.081, 95% CI: 1.007, 1.162), second trimester (RR = 1.116, 95% CI: 1.035, 1.204), third trimester (RR = 1.167, 95% CI: 1.090, 1.250) and whole pregnancy (RR = 1.098, 95% CI: 1.011, 1.192). No statistically significant RR was found for SO₂ and NO₂ on each trimester of pregnancy. Our study indicates that maternal exposure to high levels of PM_2.5 and PM₁₀ during pregnancy may increase the risk for preterm birth, especially for women at the late stage of pregnancy. Statistically increased risks of preterm birth were associated with CO exposure during each trimester and entire pregnancy. Reducing exposure to ambient air pollutants for pregnant women is clearly necessary to improve the health of infants.

A Simple Method to Establish Sufficiency and Stability in Meta-Analyses: With Application to Fine Particulate Matter Air Pollution and Preterm Birth

Fine particulate matter air pollution (PM_2.5) is a potential cause of preterm birth. Inconsistent findings from observational studies have motivated researchers to conduct more studies, but some degree of study heterogeneity is inevitable. The consequence of this feedback is a burgeoning research effort that results in marginal gains. The aim of this study was to develop and apply a method to establish the sufficiency and stability of estimates of associations as they have been published over time. Cohort studies identified in a recent systematic review and meta-analysis on the association between preterm birth and whole-pregnancy exposure to PM_2.5 were selected. The estimates of the cohort studies were pooled with cumulative meta-analysis, whereby a new meta-analysis was run for each new study published over time. The relative risks (RR) and 95% confidence interval (CI) limits needed for a new study to move the cumulative RR to 1.00 were calculated. Findings indicate that the cumulative relative risks (cRR) for PM_2.5 (cRR 1.07, 95% CI 1.03, 1.12) converged in 2015 (RR 1.07, 95% CI 1.01, 1.14). To change conclusions to a null association, a new study would need to observe a protective RR of 0.93 (95% CI limit 1.02) with precision equivalent to that achieved by all past 24 cohort studies combined. Preterm birth is associated with elevated PM_2.5, and it is highly unlikely that any new observational study will alter this conclusion. Consequently, establishing whether an observational association exists is now less relevant an objective for future studies than characterising risk (magnitude, impact, pathways, populations and potential bias) and interventions. Sufficiency and stability can be effectively applied in meta-analyses and have the potential to reduce research waste.

Prenatal PM2.5 Exposure in Relation to Maternal and Newborn Telomere Length at Delivery

Particulate matter with an aerodynamic diameter of 2.5 μm or less (PM_2.5) is a ubiquitous air pollutant that is increasingly threatening the health of adults and children worldwide. One health impact of elevated PM_2.5 exposure is alterations in telomere length (TL)-protective caps on chromosome ends that shorten with each cell division. Few analyses involve prenatal PM_2.5 exposure, and paired maternal and cord TL measurements. Here, we analyzed the association between average and trimester-specific prenatal PM_2.5 exposure, and maternal and newborn relative leukocyte TL measured at birth among 193 mothers and their newborns enrolled in a New-York-City-based birth cohort. Results indicated an overall negative relationship between prenatal PM_2.5 and maternal TL at delivery, with a significant association observed in the second trimester (β = -0.039, 95% CI: -0.074, -0.003). PM_2.5 exposure in trimester two was also inversely related to cord TL; however, this result did not reach statistical significance (β = -0.037, 95% CI: -0.114, 0.039), and no clear pattern emerged between PM_2.5 and cord TL across the different exposure periods. Our analysis contributes to a limited body of research on ambient air pollution and human telomeres, and emphasizes the need for continued investigation into how PM_2.5 exposure during pregnancy influences maternal and newborn health.

Prenatal air pollution exposure increases the risk of macrosomia: evidence from a prospective cohort study in the coastal area of China

Effects of prenatal ambient air pollution exposure could increase the risk of adverse pregnancy outcomes, which have been well documented by various studies. However, only very few studies investigated the effects on macrosomia. This study investigated the effects of prenatal air pollution exposure on the risk of macrosomia in a coastal city of China. Data of birth outcomes and air pollution in a coastal city in China between November 1, 2013, and December 31, 2017, were collected. Finally, 58,713 eligible births, including 8159 (13.9%) macrosomia and 50554 (86.1%) normal birth weight (NBW) infants, were included in the analysis. Logistic regression analyses were used to evaluate the effects of prenatal air pollution exposure on macrosomia. In the single-pollutant models, each 10 μg/m³ increase of PM_2.5, PM₁₀, and SO₂ exposures, during the entire pregnancy or three trimesters, were related to elevated risk of macrosomia (adjusted RR, 95% CI) ranging from 1.018 (1.001, 1.035) to 1.314 (1.188, 1.454). In addition, O₃ exposure in the first trimester (adjusted RR =1.034, 95% CI 1.009, 1.059) also increased the macrosomia risk. Prenatal PM_2.5, PM₁₀, and SO₂ exposure could significantly increase the risk of macrosomia. These findings need to be further verified in more studies with multiple coastal cities included.

The Asian Games, air pollution and birth outcomes in South China: An instrumental variable approach

We estimate the effects of air-pollution exposure on low birthweight, birthweight, and prematurity risk in South China, for all expectant mothers and by maternal age group and child sex. We do so by exploiting exogenous improvement in air quality during the 2010 Guangzhou Asian Games, when strict regulations were mandated to assure better air quality. We use daily air-pollution levels collected from monitoring stations in Guangzhou, the Asian Games host city, and Shenzhen, a nearby control city, between 2009 and 2011. We first show that air quality during the Asian Games significantly improved in Guangzhou, relative to Shenzhen. Next, using birth-certificate data for both cities for 2009-2011 and using expected pregnancy overlap with the Asian Games as an instrumental variable, we study the effects of three pollutants (PM₁₀, SO₂, and NO₂) on birth outcomes. Four main conclusions emerge: 1) air pollutants significantly reduce average birthweight and increase preterm risk; 2) for birthweight, late pregnancy is most sensitive to PM₁₀ exposure, but there is not consistent evidence of a sensitive period for other pollutants and outcomes; 3) for birthweight, babies of mothers who are at least 35 years old show more vulnerability to all three air pollutants; and 4) male babies show more vulnerability than female babies to PM₁₀ and SO₂, but birthweights of female babies are more sensitive than those of male babies to NO₂.

Spatially and Temporally Resolved Ambient PM2.5 in Relation to Preterm Birth

Growing evidence suggests that maternal exposure to ambient fine particulate matter (PM_2.5) during pregnancy is associated with preterm birth; however, few studies have examined critical windows of exposure, which can help elucidate underlying biologic mechanisms and inform public health messaging for limiting exposure. Participants included 891 mother-newborn pairs enrolled in a U.S.-based pregnancy cohort study. Daily residential PM_2.5 concentrations at a 1 × 1 km² resolution were estimated using a satellite-based hybrid model. Gestational age at birth was abstracted from electronic medical records and preterm birth (PTB) was defined as <37 completed weeks of gestation. We used Critical Window Variable Selection to examine weekly PM_2.5 exposure in relation to the odds of PTB and examined sex-specific associations using stratified models. The mean ± standard deviation PM_2.5 level averaged across pregnancy was 8.13 ± 1.10 µg/m³. PM_2.5 exposure was not associated with an increased odds of PTB during any gestational week. In sex-stratified models, we observed a marginal increase in the odds of PTB with exposure occurring during gestational week 16 among female infants only. This study does not provide strong evidence supporting an association between weekly exposure to PM_2.5 and preterm birth.

Maternal air pollution exposure increases the risk of preterm birth: Evidence from the meta-analysis of cohort studies

Preterm birth (PTB), a major public health impact, has been shown to be associated with prenatal air pollution exposure, but the results are still inconsistent. This meta-analysis was performed to quantitatively evaluate the correlation between maternal air pollutant exposure and PTB, and provide evidence of higher grade to help improving the pregnancy outcomes. Databases including Web of Science and PubMed were searched to retrieve eligible studies published up to October 2020. The quality of the articles was assessed by the Newcastle-Ottawa Quality Score (NOS), after which the pooled estimate of the effect was calculated. The robustness of the joint estimates was confirmed by sensitivity analysis of excluded studies one by one, and the sources of heterogeneity were discussed by stratification analysis. Egger's and Begg's tests were performed to examine publication bias. Sixty studies that met the eligible criteria were finally included in this study. The findings showed combined relative risks of 1.032-1.070 for PTB, 0.859-1.081 for moderate PTB, 1.119-1.194 for very PTB and 1.128-1.259 for extremely PTB when mothers were exposed to PM_2.5, PM₁₀, NO₂, O₃, SO₂, CO and NO_x during pregnancy, while the sensitive windows varied for different air pollutants. Notably, PM_2.5 exposure in only the 2nd trimester, NO₂ exposure in only the 3rd trimester, and O₃ exposure in all three trimesters were positively associated with PTB, while NO₂ exposure in the 1st trimester was negatively associated with PTB. In addition, exposure of PM_2.5 and PM₁₀ in the 2nd trimester was positively associated with moderate PTB, and in the 1st and 2nd trimesters were positively associated with very PTB. These findings demonstrated that PM_2.5, PM₁₀, O₃, NO₂ were associated with PTB (including moderate PTB, very PTB, and/or extremely PTB), while NO_x was not, and the relationship between CO and SO₂ and PTB was not stable.

Exploring common factors influencing PM2.5 and O3 concentrations in the Pearl River Delta: Tradeoffs and synergies

Particulate matter with an aerodynamic equivalent dimeter less than 2.5 μm (PM_2.5) and ozone (O₃) are major air pollutants, with coupled and complex relationships. The control of both PM_2.5 and O₃ pollution requires the identification of their common influencing factors, which has rarely been attempted. In this study, land use regression (LUR) models based on the least absolute shrinkage and selection operator were developed to estimate PM_2.5 and O₃ concentrations in China's Pearl River Delta region during 2019. The common factors in the tradeoffs between the two air pollutants and their synergistic effects were analyzed. The model inputs included spatial coordinates, remote sensing observations, meteorological conditions, population density, road density, land cover, and landscape metrics. The LUR models performed well, capturing 54-89% and 42-83% of the variations in annual and seasonal PM_2.5 and O₃ concentrations, respectively, as shown by the 10-fold cross validation. The overlap of variables between the PM_2.5 and O₃ models indicated that longitude, aerosol optical depth, O₃ column number density, tropospheric NO₂ column number density, relative humidity, sunshine duration, population density, the percentage cover of forest, grass, impervious surfaces, and bare land, and perimeter-area fractal dimension had opposing effects on PM_2.5 and O₃. The tropospheric formaldehyde column number density, wind speed, road density, and area-weighted mean fractal dimension index had complementary effects on PM_2.5 and O₃ concentrations. This study has improved our understanding of the tradeoff and synergistic factors involved in PM_2.5 and O₃ pollution, and the results can be used to develop joint control policies for both pollutants.

Association between maternal exposure to gaseous pollutants and atrial septal defect in China: A nationwide population-based study

BACKGROUND

The association between maternal exposure to gaseous air pollutants and congenital heart defects (CHD) remains unclear. The concentration-response relationship and the time windows of susceptibility to gaseous pollutants may vary by pollutant species and CHD subtypes.

OBJECTIVE

We aimed to examine the relationship between maternal exposures to four species of gaseous pollutants (NO₂, O₃, SO₂, and CO) and atrial septal defect (ASD), which is a common subtype of CHD, and to determine the critical time windows of susceptibility for each gaseous pollutant.

METHODS

Among 1,253,633 infants born between October 1, 2013 and December 31, 2016 in China, 1937 newborns were diagnosed with isolated ASD, a prevalence of 1.55‰. Maternal exposures to the gaseous pollutants were estimated by matching the geocoded maternal addresses with the gridded ambient concentrations. The adjusted odds ratios (aOR) between exposures and ASD were quantified by using mixed-effects logistic regression models.

RESULTS

We found significantly positive associations between ASD and maternal exposures to NO₂, O₃, SO₂, and CO during entire pregnancy, first-, second-, and third-trimester. However, no statistically significant association was found between maternal exposure to PM_2.5, PM_2.5-10 and ASD risk (P > 0.05). In the fully adjusted model with respect to average exposure over entire pregnancy, the adjusted odds ratios (aOR) for each 10 μg/m³ increment of NO₂, O₃, SO₂ were 1.33 (95% CI: 1.22-1.45), 1.13 (95% CI: 1.10-1.16), 1.28 (95% CI: 1.20-1.35), respectively; the aOR for each 100 μg/m³ increment of CO was 1.10 (95% CI: 1.06-1.15). The observed concentration-response relationships varied by exposure periods and pollutants, with the strongest association for NO₂ during the 1st-8th embryology weeks, for O₃ during the third trimester, for SO₂ during the second trimester, and for CO without obvious variation.

CONCLUSIONS

The findings suggest an increased risk of ASD in association with maternal exposures to four common gaseous pollutants. From the perspective of birth defects prevention and ASD risk mitigation, it is critical to reduce maternal exposure to gaseous pollutants especially during the most susceptible time windows.

Weekly-specific ambient fine particular matter exposures before and during pregnancy were associated with risks of small for gestational age and large for gestational age: results from Project ELEFANT

BACKGROUND

Investigations on the potential effects of ambient fine particulate matter (PM2.5) on large for gestational age (LGA) are limited. Furthermore, no study has explored weekly-specific susceptible exposure windows for small for gestational age (SGA) and LGA. This study evaluated the associations of exposure to ambient PM2.5 over the preconception and entire-pregnancy periods with risks of SGA and LGA, as well as explored critical weekly-specific exposure windows.

METHODS

10 916 singleton pregnant women with 24-42 completed gestational weeks from the Project Environmental and LifEstyle FActors iN metabolic health throughout life-course Trajectories between 2014 and 2016 were included in this study. Distributed lag models (DLMs) incorporated in Cox proportional-hazards models were applied to explore the associations of maternal exposure to weekly ambient PM2.5 throughout 12 weeks before pregnancy and pregnancy periods with risks of SGA and LGA after controlling for potential confounders.

RESULTS

For a 10-μg/m3 increase in maternal exposure to PM2.5, positive associations with SGA were observed during the 1st to 9th preconceptional weeks and the 1st to 2nd gestational weeks (P<0.05), with the strongest association in the 5th preconceptional week [hazard ratio (HR), 1.06; 95% confidential interval (CI), 1.03-1.09]. For LGA, positive associations were observed during the 1st to 12th preconceptional weeks and the 1st to 5th gestational weeks (P<0.05), with the strongest association in the 7th preconceptional week (HR, 1.10; 95% CI, 1.08-1.12).

CONCLUSIONS

Exposure to high-level ambient PM2.5 is associated with increased risks of both SGA and LGA, and the most susceptible exposure windows are the preconception and early-pregnancy periods.

Long-term exposure to ambient PM2.5 increase obesity risk in Chinese adults: A cross-sectional study based on a nationwide survey in China

Certain studies suggest that air pollution could be a risk factor for obesity, but the evidence on the association between air pollution exposure and obesity in adults is limited. This study aims to examine the association between long-term exposure to fine particulate matter (PM_2.5) and obesity-related traits in Chinese adults. Thus, a cross-sectional study was conducted based on a nationally representative sample of 91, 121 adults from 31 provinces in China. Integrated the data from satellites, chemical transport model, and ground observations, annual average concentrations of PM_2.5 was obtained at the township level using a machine learning method. The information on body weight, height, and waist circumference (WC) were obtained from a questionnaire survey. The general obesity and abdominal obesity status were classified based on body mass index (BMI) and WC, respectively. Logistic and multivariate linear regression models were used to examine the association between PM_2.5 and obesity-related traits, along with the examination of potential effect modifications. After adjustment for covariates, a 10 μg/m³ increase in PM_2.5 concentration was associated with 8.0% [95% confidence interval (CI): 1.0%, 10.0%] and 10% (95% CI: 9.0%, 11.0%) increases in odds for general obesity and abdominal obesity, respectively. The odds ratios associated with per 10 μg/m³ PM_2.5 increase were significantly greater in individuals of older age (≥60 years), of Han ethnicity, with lower socioeconomic status (SES), cooking without using a ventilation device, using unclean household fuels, having near-home pollution sources, and doing no physical exercise. These findings suggest that long-term exposure to ambient PM_2.5 increase obesity risk in Chinese adults. It has significant significance to reduce air pollution to reducing the burden of obesity, particularly for the susceptible populations.

Maternal exposure to sulfur dioxide before and after conception and the risk of hypospadias in offspring

As far as we know, there have been no studies exploring the association between maternal sulfur dioxide (SO₂ ) exposure and the risk of hypospadias in offspring. We aimed to evaluate this association during the 3 months before conception and the first trimester. A population-based case-control study was conducted in male infants, consisting of 348 cases of hypospadias and 4023 controls. Maternal exposure to SO₂ , particulate matter with aerodynamic diameters ≤10 μm (PM₁₀ ), and nitrogen dioxide (NO₂ ) was assessed by averaging the concentrations recorded at all stations in the mother's city of residence. Air pollutants were tested for multicollinearity using variance inflation factor analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by multivariable logistic regression models. SO₂ exposure during the 3 months before conception was significantly associated with the risk of hypospadias (highest tertile: OR = 7.40, 95% CI: 3.54-15.62). When focusing on shorter exposure windows, similar associations were observed for SO₂ exposure in the first and second month before and the first month after conception. In conclusion, maternal exposure to SO₂ during the 3 months before and the first and second months after conception may increase the risk of hypospadias in offspring.

Ozone exposure during early pregnancy and preterm birth: A systematic review and meta-analysis

Exposure to ozone has been linked to reproductive outcomes, including preterm birth. In this systematic review, we summarize published epidemiologic cohort and case-control studies examining ozone exposures (estimated on a continuous scale) in early pregnancy (1st and 2nd trimesters (T1, T2)) and preterm birth using ratio measures, and perform a meta-analysis to evaluate the potential relationship between them. Studies were identified by searching PubMed and Web of Science, screened according to predefined inclusion/exclusion criteria, and evaluated for study quality. We extracted study data including effect estimates, confidence limits, study location, study years, ozone exposure assessment method, and mean or median ozone concentrations. Nineteen studies were identified and included, of which 18 examined T1 exposure (17 reported effect estimates), and 15 examined T2 exposure. Random effects meta-analysis was performed in the metafor package, R 3.5.3. The pooled OR (95% CI) for a 10 ppb increase in ozone exposure in T1 was 1.06 (1.03, 1.10) with a 95% prediction interval of 0.95, 1.19; for T2 it was 1.05 (1.02, 1.08) with a 95% prediction interval of 0.95, 1.16. Effect estimates for both exposure periods showed high heterogeneity. In meta-regression analyses of study characteristics, study location (continent) explained some (~20%) heterogeneity for T1 exposure studies, but no characteristic explained a substantial amount of heterogeneity for T2 exposure studies. Increased ozone exposure during early pregnancy is associated with preterm birth across studies.

Maternal PM2.5 exposure associated with stillbirth: A large birth cohort study in seven Chinese cities

BACKGROUND

Maternal exposure to fine particulate matter (PM_2.5) has been associated with a few adverse birth outcomes. However, its effect on stillbirth remains unknown in China, especially the susceptible windows and potential modifiers.

OBJECTIVE

This study aimed to evaluate the associations between maternal PM_2.5 exposure and stillbirth in seven Chinese cities.

METHODS

We used birth cohort data of 1,273,924 mother-and-birth pairs in seven cities in southern China between 2014 and 2017 to examine these associations. Pregnant women were recruited in the cohort at their first visit to a doctor for pregnancy, and stillbirths were recorded at the time of birth. Air pollution exposures were assessed through linking daily air pollutant concentrations from nearby monitoring stations to the mother's residential community. Cox regression models were applied to determine the associations between PM_2.5 and stillbirth for different gestational periods.

RESULTS

Among the participants, 3150 (2.47‰) were identified as stillbirth cases. The hazard ratio (HR) of stillbirths was 1.52 (95% CI: 1.42, 1.62) for each 10 μg/m³ increase in PM_2.5 during the entire pregnancy after controlling for some important covariates. Relatively stronger associations were observed during the second trimester [adjusted HR = 1.67 (95% CI: 1.57, 1.77)] than trimesters 1 [HR = 1.44 (95% CI: 1.37, 1.52)] and trimester 3 [HR = 1.23 (95% CI: 1.16, 1.30)]. Stratified analyses also showed a stronger association among pregnant women without previous pregnancy and previous delivery experiences.

CONCLUSION

The study indicates that maternal exposure to PM_2.5, especially during the midpoint period of pregnancy, might increase the risk of stillbirths. Maternal previous pregnancy and delivery may modify this association.

Effect of air temperature on human births, preterm births and births associated with maternal hypertension

OBJECTIVE

We studied potential effects of outdoor air temperatures or barometric pressure on births, preterm births and births associated with maternal hypertension.

METHODS

12,269 births were retrospectively reviewed in Brussel and 25,880 in South Reunion Island. National Belgium and French weather reference centers provided outdoor air temperatures and barometric pressures from the nearest weather stations on the corresponding birthdays. Poisson regression models were used to assess if outdoor air temperatures or barometric pressure could be correlated, immediately and several days later, with the number of daily births, preterm births and births associated with hypertension.

RESULTS

Outdoor air temperature was significantly correlated to the number of daily births in Brussels. For each additional degree Celsius, overall births increased by 0.4% during the same day. Four days later, overall births increased by 1.8%, preterm births by 2.6% and births associated with hypertension by 5.7%. Similar observations on numbers of daily births were reported in South Reunion Island, without reaching statistical significance (p = .08).

CONCLUSION

As previously demonstrated in recent studies, increased air temperature leads progressively to higher rates of births and preterm births. An even stronger delayed effect of air temperature was observed on births associated with hypertension. This would be worth further investigating.

The Association between Preterm Birth and Ambient Air Pollution Exposure in Shiyan, China, 2015-2017

Shortening of the gestational duration has been found associated with ambient air pollution exposure. However, the critical exposure windows of ambient air pollution for gestational duration remain inconsistent, and the association between ambient air pollution and early term births (ETB, 37 to 38 weeks) has rarely been studied relative to preterm births (PTB, 28–37 weeks). A time-series study was conducted in Shiyan, a medium-sized city in China. Birth information was collected from the Shiyan Maternity and Child Health Hospital, and 13,111 pregnant women who gave birth between 2015 and 2017 were included. Data of the concentrations of air pollutants, including PM₁₀, PM_2.5, NO₂, and SO₂ and meteorological data, were collected in the corresponding gestational period. The Cox regression analysis was performed to estimate the relationship between ambient air pollution exposure and the risk of preterm birth after controlling the confounders, including maternal age, education, Gravidity, parity, fetal gender, and delivery mode. Very preterm birth (VPTB, 28–32 weeks) as a subtype of PTB was also incorporated in this study. The risk of VPTB and ETB was positively associated with maternal ambient air pollution exposure, and the correlation of gaseous pollutants was stronger than particulate matter. With respect to exposure windows, the critical trimester of air pollutants for different adverse pregnancy outcomes was different. The exposure windows of PM₁₀, PM_2.5, and SO₂ for ETB were found in the third trimester, with HRs (hazard ratios) of 1.06 (95%CI: 1.04, 1.09), 1.07 (95%CI: 1.04, 1.11), and 1.28 (95%CI: 1.20, 1.35), respectively. However, for NO₂, the second and third trimesters exhibited similar results, the HRs reaching 1.10 (95%CI: 1.03, 6.17) and 1.09 (95%CI: 1.03,1.15), respectively. This study extends and strengthen the evidence for a significant correlation between the ambient air pollution exposure during pregnancy and the risk of not only PTB but, also, ETB. Moreover, our findings suggest that the exposure windows during pregnancy vary with different air pollutants and pregnancy outcomes.

Associations of adverse pregnancy outcomes with high ambient air pollution exposure: Results from the Project ELEFANT

BACKGROUND

Investigations on the potential effects of high air pollution exposure before pregnancy on adverse pregnancy outcomes are limited, and it is unknown whether air quality standards looser than that set by World Health Organization (WHO) still can provide sufficient protection pregnant women from adverse pregnancy outcomes.

OBJECTIVES

To evaluate the potential effects of high ambient air pollution around pregnancy on preterm birth (PTB) and low birth weight (LBW), and assess the risk of PTB and LBW associated with air pollutants with reference to different air quality standards of WHO and China.

METHODS

Our study leveraged 10,960 pregnant women from the Project ELEFANT. Daily average particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO) and ozone (O₃) concentrations were collected based on Chinese Air Quality Reanalysis datasets. Hazard ratios (HR) of PTB and LBW were estimated for maternal PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃ exposures and related proportions of days with daily average air pollution concentrations exceeding air quality standards of WHO and China around pregnancy using Cox proportional hazards regression models with adjustment for potential confounders.

RESULTS

Ambient PM_2.5, PM₁₀, NO₂, SO₂ and CO exposure during the before pregnancy and pregnancy period were both significantly and positively associated with increased risk of PTB, PTB subtypes and LBW. A 10% increase in proportion of days with daily average PM_2.5 exceeding 25 μg/m³ over the entire pregnancy was most apparently associated with risk of PTB (HR, 12.66; 95% CI, 8.20-19.53) and LBW (HR, 17.42; 95% CI, 6.88-44.10) among all PM_2.5 proportion variables based on different air quality standards.

CONCLUSION

Air quality standards of WHO are necessary to be implemented to control for risks of adverse pregnancy outcomes associated with ambient air pollution in areas with high air pollution levels.

Association of Preterm Birth with Depression and Particulate Matter: Machine Learning Analysis Using National Health Insurance Data

This study uses machine learning and population data to analyze major determinants of preterm birth including depression and particulate matter. Retrospective cohort data came from Korea National Health Insurance Service claims data for 405,586 women who were aged 25–40 years and gave births for the first time after a singleton pregnancy during 2015–2017. The dependent variable was preterm birth during 2015–2017 and 90 independent variables were included (demographic/socioeconomic information, particulate matter, disease information, medication history, obstetric information). Random forest variable importance was used to identify major determinants of preterm birth including depression and particulate matter. Based on random forest variable importance, the top 40 determinants of preterm birth during 2015–2017 included socioeconomic status, age, proton pump inhibitor, benzodiazepine, tricyclic antidepressant, sleeping pills, progesterone, gastroesophageal reflux disease (GERD) for the years 2002–2014, particulate matter for the months January–December 2014, region, myoma uteri, diabetes for the years 2013–2014 and depression for the years 2011–2014. In conclusion, preterm birth has strong associations with depression and particulate matter. What is really needed for effective prenatal care is strong intervention for particulate matters together with active counseling and medication for common depressive symptoms (neglected by pregnant women).

Association between maternal outdoor physical exercise and the risk of preterm birth: a case-control study in Wuhan, China

BACKGROUND

China had the second largest proportion of preterm birth (PTB) internationally. However, only 11% of pregnant women in China meet international guidelines for maternal physical activity, a significantly lower proportion than that in Western countries. This study aims to examine the association between outdoor physical exercise during pregnancy and PTB among Chinese women in Wuhan, China.

METHODS

A case-control study was conducted among 6656 pregnant women (2393 cases and 4263 controls) in Wuhan, China from June 2011 to June 2013. Self-reported measures of maternal physical exercise (frequency per week and per day in minutes) were collected. Adjusted odds ratios were estimated using Bayesian hierarchical logistic regression and a generalized additive mixed model (GAMM).

RESULTS

Compared to women not involved in any physical activity, those who participated in physical exercise 1-2 times, 3-4 times, and over five times per week had 20% (aOR: 0.80, 95% credible interval [95% CI]: 0.68-0.92), 30% (aOR: 0.70, 95% CI: 0.60-0.82), and 32% (aOR: 0.68, 95% CI: 0.59-0.78) lower odds of PTB, respectively. The Bayesian GAMM showed that increasing physical exercise per day was associated with lower risk of PTB when exercise was less than 150 min per day; however, this direction of association is reversed when physical exercise was more than 150 min per day.

CONCLUSION

Maternal physical exercise, at a moderate amount and intensity, is associated with lower PTB risk. More data from pregnant women with high participation in physical exercise are needed to confirm the reported U-shape association between the physical exercise and risk of preterm birth.

Prenatal exposure to air pollutants and early childhood growth trajectories: A population-based prospective birth cohort study

BACKGROUND

Air pollution exposure during pregnancy has been documented to be associated with impaired fetal growth and adverse birth outcomes, but the evidence regarding the effects of air pollution on early childhood growth is still limited.

OBJECTIVE

We aimed to explore the associations of exposure to air pollutants during pregnancy with childhood growth trajectories from birth to age of 6 years.

METHODS

A prospective cohort study based on the administrative registration system was conducted covering 62,540 births in Wuhan, China between January 1, 2011 and December 31, 2013 and followed for 6 years. Inverse distance weighted method was used to estimate the concentrations of air pollutants exposure for pregnant women. Group-based trajectory models (GBTM) were used to identify growth patterns of children: slow growth, normal growth, and rapid growth. Multinomial logistic regression models were used to examine the associations between prenatal exposure to air pollutants and childhood growth trajectories with adjustment for maternal age, educational status, pre-pregnancy BMI, residential areas, gestational diabetes, birth type, gender of infant, and breastfeeding duration.

RESULTS

The mean (SD) of prenatal exposure concentrations for PM₁₀, SO₂, NO₂, CO, and O₃ were 107.9 (30.4), 32.8(12.6), 55.8(13.1), 1081.2(293.1), and 81.6(31.0) μg/m³ respectively. Compared with normal growth trajectory, increased PM₁₀ and CO exposure were significantly associated with higher risk of slow growth trajectory but lower risk of rapid growth trajectory. An increase in prenatal exposure to NO₂ significantly increased both the risk of slow growth trajectory and rapid growth trajectory. Increased prenatal SO₂ exposure was significantly associated with rapid growth trajectory and was not associated with low growth trajectory. With O₃ exposure levels increased, risk to be rapid growth trajectory decreased. Prenatal air pollutants exposure had a greater impact on childhood growth of children who were girls, and those mothers lived in rural areas and were normal weight before pregnancy.

CONCLUSIONS

High levels of air pollutants exposure during pregnancy were associated with the risk of being in a trajectory with the deviation of BMI gain from birth to 6 years old. These findings suggest that efforts to identify children at risk of growth deviation in early childhood should pay attention to environmental exposure during pregnancy for their mothers.