Preterm birth and air pollution: Critical windows of exposure for women with asthma

Traffic-related air pollution is associated with spontaneous extremely preterm birth and other adverse perinatal outcomes

BACKGROUND

Although there is growing awareness of the relationship between air pollution and preterm birth, limited data exist regarding the relationship with spontaneous preterm birth and severe neonatal outcomes.

OBJECTIVE

This study aimed to examine the association between traffic-associated air pollution exposure in pregnancy and adverse perinatal outcomes including extremes of preterm birth, neonatal intensive care unit admissions, low birthweight, neonatal respiratory diagnosis, neonatal respiratory support, and neonatal sepsis evaluation.

STUDY DESIGN

This was a retrospective cohort study of singleton pregnancies of patients residing in a metropolitan area in the southern United States. Using monitors strategically located across the region, average nitrogen dioxide concentrations were obtained from the Environmental Protection Agency Air Quality System database. For patients living within 10 miles of a monitoring station, average exposure to nitrogen dioxide was estimated for individual patients' pregnancy by trimester. Logistic regression models were used to assess the effect of pollutant exposure on gestational age at birth, indicated vs spontaneous delivery, and neonatal outcomes while adjusting for maternal age, self-reported race, parity, season of conception, diabetes mellitus, body mass index, registered Health Equity Index, and nitrogen dioxide monitor region. Adjusted odds ratios and 95% confidence intervals were calculated for an interquartile increase in average nitrogen dioxide exposure.

RESULTS

Between January 1, 2013 and December 31, 2021, 93,164 patients delivered a singleton infant. Of these, 62,189 had measured nitrogen dioxide exposure during the pregnancy from a nearby monitoring station. Higher average nitrogen dioxide exposure throughout pregnancy was significantly associated with preterm birth (adjusted odds ratio, 1.94; 95% confidence interval, 1.77-2.12) and an increase in neonatal intensive care unit admissions, low birthweight infants, neonatal respiratory diagnosis, neonatal respiratory support, and neonatal sepsis evaluation. This relationship persisted for nulliparous patients and spontaneous preterm birth, and had a greater association with earlier preterm birth.

CONCLUSION

In a metropolitan area, increased exposure to the air pollutant nitrogen dioxide in pregnancy was associated with spontaneous preterm birth and had a greater association with extremely preterm birth. A greater association with neonatal intensive care unit admissions, low-birthweight infants, neonatal respiratory diagnosis, neonatal respiratory support, and neonatal sepsis evaluation was found even in term infants.

Cigarette smoke-induced injury induces distinct sex-specific transcriptional signatures in mice tracheal epithelial cells

The airway epithelial barrier is crucial for defending against respiratory insults and diseases. Disruption of epithelial integrity contributes to respiratory diseases, and sex-specific differences in susceptibility and severity have been observed. However, sex-specific differences in the context of respiratory diseases are often overlooked, especially in murine models. In this study, we investigated the in vitro transcriptomics of male and female murine tracheal epithelial cells (mTECs) in response to chronic cigarette smoke (CS) exposure using an International Organization for Standardization (ISO) puff regimen. Our findings reveal sex-specific differences in the baseline characteristics of airway epithelial cells. Female mTECs demonstrated stronger barrier function and higher ciliary function compared with males. The barrier function was disrupted in both males and females following chronic CS, but the difference was more significant in females due to their higher baseline. Female mice exhibited transcriptional signatures suggesting dedifferentiation with increased basal cells and markers of cellular senescence. Pathway analysis indicated potential protective roles of planar cell polarity (PCP) in preventing dedifferentiation in male mice exposed to CS. We also observed sex-specific differences in the DNA damage response and antioxidant levels, suggesting distinct mechanisms underlying cellular stress. Understanding these sex-specific mechanisms could facilitate the development of targeted therapeutic strategies for lung diseases associated with environmental insults. Recognizing sex-based differences in disease susceptibility and treatment response can lead to personalized care and improved outcomes. Clinical trials should consider sex as a biological variable to develop effective interventions that address the unique differences between men and women in respiratory diseases.NEW & NOTEWORTHY The study underscores the importance of considering sex-specific differences in the airway epithelium in respiratory diseases such as COPD. Differences in gene expression between males and females at baseline and in response to chronic injury in the airway epithelium could have implications on disease susceptibility, both in COPD and other respiratory diseases. Therefore, understanding these differences is crucial for developing targeted therapies to treat respiratory diseases based on a sex-specific manner.

Chronic Management of Asthma During Pregnancy

Asthma is one of the most common potentially serious medical problems to complicate pregnancy. Optimal management of asthma during pregnancy is thus important for both mother and baby. Treating asthmatic women requires understanding the effects of pregnancy on the course of asthma, and, conversely, the effects of asthma on pregnancy outcomes. Successful management also requires an understanding the barriers to asthma control in this population of patients. Evidence has shown that it is essential that the allergist-immunologist, obstetrician, and patient work as a team during pregnancy to achieve optimal maternal and neonatal outcomes.

A systematic review of evidence for maternal preconception exposure to outdoor air pollution on Children's health

The preconception period is a critical window for gametogenesis, therefore preconception exposure to air pollutants may have long-term effects on children. We systematically reviewed epidemiological evidence concerning the effects of preconception ambient air pollution exposure on children's health outcomes and identified research gaps for future investigations. We searched PubMed and Web of Science from journal inception up to October 2022 based on an established protocol (PROSPERO: CRD42022277608). We then identified 162 articles based on searching strategy, 22 of which met the inclusion criteria. Studies covered a wide range of health outcomes including birth defects, preterm birth, birthweight, respiratory outcomes, and developmental outcomes. Findings suggested that exposure to outdoor air pollutants during maternal preconception period were associated with various health outcomes, of which birth defects has the most consistent findings. A meta-analysis revealed that during 3-month preconception period, a 10 μg/m3 increase in PM10 and PM2.5 was associated with relative risk (RR) of birth defects of 1.06 (95% confidence interval (CI): 1.00, 1.02) and 1.14 (95% CI: 0.82, 1.59), respectively. Preterm birth, low birthweight, and autism have also been associated with maternal preconception exposure to PM2.5, PM10, O3 and SO2. However, the significance of associations and effect sizes varied substantially across studies, partly due to the heterogeneity in exposure and outcome assessments. Future studies should use more accurate exposure assessment methods to obtain individual-level exposures with high temporal resolution. This will allow the exploration of which specific time window (weeks or months) during the preconception period has the strongest effect. In future epidemiologic studies, integrating pathophysiologic biomarkers relevant to clinical outcomes may help improve the causal inference of associations between preconception exposure and health outcomes suggested by the current limited literature. Additionally, potential effects of paternal preconception exposure need to be studied.

A time series analysis of ambient air pollution and low birth weight in Xuzhou, China

The objective of this study was to examine the relationship between weekly specific maternal air pollution exposures and low birth weight. We fitted a distributed lag nonlinear model (DLNM) to analyze the nonlinear exposure-response association and delayed effects of air pollutants on the risk for low birth weight. The model assumed that all live births have 40 gestational weeks.The 1st week lag was the 40th gestational week, and 40th lag week was the 1st gestational week.The study included 71,809 live births (from July 1, 2016, to June 30, 2019), of which 2,391 (3.33%) exhibited low birth weight. The results demonstrated that exposure of pregnant women to PM10 at lag 22-30 weeks was significantly associated with low birth weight risk, with the greatest impact at the lag 30 week. Exposure to SO2 at lag 29-37 weeks was significantly associated with low birth weight risk. The sensitive exposure window for NO2 began at lag 25-37 weeks of pregnancy. The lag 6-10 weeks constituted the susceptible exposure window for O3. Therefore we concluded that maternal exposures to PM10, SO2, NO2, and O3 were associated with increased risk for low birth weight.

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.

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.

World Prematurity Day: it takes an NIH village to prevent preterm birth and improve treatments for preterm infants

Prematurity remains a major cause of morbidity and mortality. Research to prevent preterm birth and improve treatments for preterm infants involves both intramural and extramural research, not just at the National Institute of Child Health and Human Development, but across many institutes and centers at the National Institutes of Health.

Country-based report: the safety of omalizumab treatment in pregnant patients with asthma

BACKGROUND/AIM

We aimed to report outcomes of pregnant patients with asthma under omalizumab treatment and their infants in our country.

MATERIALS AND METHODS

Patients with asthma who received omalizumab for at least 6 months and at least one dose during their pregnancy were retrospectively evaluated using a questionnaire regarding their disease and therapy and the health of their infants.

RESULTS

Twenty pregnant patients and their 23 infant’s data were analyzed. The mean delivery age was 31.8 ± 7.4 years. They received omalizumab for 28.9 ± 21.8 months. Eight (36.4%) patients showed exacerbation of the disease during pregnancy. Forced expiratory volume in 1 s (FEV1) and asthma control test (ACT) scores at the starting time of omalizumab administration, first month of the pregnancy, and after delivery were 71 ± 18%, 83.4 ± 10.5%, and 80.5 ± 13% (FEV1), and 11.9 ± 4.9, 20.2 ± 2.6, and 20.4 ± 2.2 (ACT), respectively. One patient gave birth to twin infants, two patients to two infants each in different years, and 17 to one infant each. Three (13%) infants had low birth weight and five (21.7%) were born prematurely. No congenital anomalies were detected. Seven (30.4%) infants presented atopic diseases during their life.

CONCLUSION

Omalizumab treatment during pregnancy seems to be safe for both patients and their infants.

Air pollution exposure and risk of adverse obstetric and neonatal outcomes among women with type 1 diabetes

AIMS/HYPOTHESIS

Women with type 1 diabetes have increased risk for poor obstetric outcomes. Prenatal air pollution exposure is also associated with adverse outcomes for women and infants. We examined whether women with type 1 diabetes are more vulnerable than other women to pollution-associated risks during pregnancy.

METHODS

In singleton deliveries from the Consortium on Safe Labor (2002-2008), obstetric and neonatal outcomes were compared for women with type 1 diabetes (n = 507) and women without autoimmune disease (n = 204,384). Preconception, trimester, and whole pregnancy average air pollutant exposure (ozone (O₃), carbon monoxide (CO), particulate matter >10 μm (PM₁₀), PM > 2.5 μm (PM_2.5), sulfur dioxide (SO₂), nitrogen oxides (NO_x)) were estimated using modified Community Multiscale Air Quality models. Poisson regression models with diabetes*pollutant interaction terms estimated relative risks and 95% confidence intervals for adverse outcomes, adjusted for maternal characteristics and geographic region.

RESULTS

For whole pregnancy exposure to SO₂, women with type 1 diabetes had 15% increased risk (RR:1.15 95%CI:1.01,1.31) and women without autoimmune disease had 5% increased risk (RR:1.05 95%CI:1.05,1.06) for small for gestational age birth (p_interaction = 0.09). Additionally, whole pregnancy O₃ exposure was associated with 10% increased risk (RR:1.10 95%CI:1.02,1.17) among women with type 1 diabetes and 2% increased risk (RR:1.02 95%CI:1.00,1.04) among women without autoimmune disease for perinatal mortality (p_interaction = 0.08). Similar patterns were observed between PM_2.5 exposure and spontaneous preterm birth.

CONCLUSIONS

Pregnant women with type 1 diabetes may be at greater risk for adverse outcomes when exposed to air pollution than women without autoimmune disease.

[Management of asthma during pregnancy]

Asthma is the most common chronic condition in pregnant women. The risks of complications associated with asthma for the mother, the foetus and the pregnancy are mainly due to uncontrolled asthma and the occurrence of exacerbations. These events are promoted by the patient's difficulty in complying with treatment or by prescription insufficiency for an unjustified fear of teratogenicity. The challenge of the management of asthma during pregnancy is to ensure optimal maternal asthma control in order to prevent foetal hypoxia and thus, reduce the risk of complications. Preventing the occurrence of asthma symptoms and exacerbations, ensuring optimal lung function and managing the risk factors of poor asthma outcomes and comorbidities are the principles necessary to achieve this goal. Because of the low or non-existent risks of the main treatments of asthma for the foetus and the mother, it is widely recommended that all therapies initiated before conception are continued, in particular inhaled corticosteroids, and to adjust the dosage to the minimum effective dose. During the preconception period and throughout pregnancy, coordination of the different healthcare professionals (general practitioner, respiratory specialist and gynecologist) is essential, with the mother-to-be playing a central role in the management of her asthma.

"Something Was Attacking Them and Their Reproductive Organs": Environmental Reproductive Justice in an Indigenous Tribe in the United States Gulf Coast

Environmental reproductive justice is increasingly being utilized as a framework for exploring how environmental exploitation and pollution contribute to reproductive health and reproductive injustices. However, little research explores how settler colonialism and historical oppression contribute to the physical transformation of land, and how this undermines tribal members' health. Even less research explores the intersection of environmental justice and reproductive justice among Indigenous groups, especially in the Gulf South, who are especially vulnerable to environmental justice issues due to climate change, land loss, and oil company exploitation, and for tribes that are non-federally recognized. A qualitative description research methodology was used to conduct 31 life-history interviews with women from a Gulf Coast Indigenous tribe. Findings of this study reveal that central components of reproductive justice, including the ability to have children and the ability to raise children in safe and healthy environments, are undermined by environmental justice issues in the community. Among concerns raised by women were high rates of chronic healthcare issues among community members, and issues with infertility. Recognizing Indigenous sovereignty is central to addressing these environmental reproductive justice issues. This research is unique in exploring the topic of environmental reproductive justice among a state-recognized Gulf Coast tribe.

Air Pollution Exposure Monitoring among Pregnant Women with and without Asthma

Background: We monitored exposure to fine particulates (PM_2.5), ozone, nitrogen dioxide (NO₂), and ambient temperature for pregnant women with and without asthma. Methods: Women (n = 40) from the Breathe—Well-Being, Environment, Lifestyle, and Lung Function Study (2015–2018) were enrolled during pregnancy and monitored for 2–4 days. Daily pollutants were measured using personal air monitors, indoor air monitors, and nearest Environmental Protection Agency’s stationary monitors based on GPS tracking and home address. Results: Personal-monitor measurements of PM_2.5, ozone, and NO₂ did not vary by asthma status but exposure profiles significantly differed by assessment methods. EPA stationary monitor-based methods appeared to underestimate PM_2.5 and temperature exposure and overestimate ozone and NO₂ exposure. Higher indoor-monitored PM_2.5 exposures were associated with smoking and the use of gas appliances. The proportion of waking-time during which personal monitors were worn was ~56%. Lower compliance was associated with exercise, smoking, being around a smoker, and the use of a prescription drug. Conclusions: Exposure did not vary by asthma status but was influenced by daily activities and assessment methods. Personal monitors may better capture exposures but non-compliance merits attention. Meanwhile, larger monitoring studies are warranted to further understand exposure profiles and the health effects of air pollution during pregnancy.

Association of Air Pollution and Heat Exposure With Preterm Birth, Low Birth Weight, and Stillbirth in the US: A Systematic Review

IMPORTANCE

Knowledge of whether serious adverse pregnancy outcomes are associated with increasingly widespread effects of climate change in the US would be crucial for the obstetrical medical community and for women and families across the country.

OBJECTIVE

To investigate prenatal exposure to fine particulate matter (PM2.5), ozone, and heat, and the association of these factors with preterm birth, low birth weight, and stillbirth.

EVIDENCE REVIEW

This systematic review involved a comprehensive search for primary literature in Cochrane Library, Cochrane Collaboration Registry of Controlled Trials, PubMed, ClinicalTrials.gov website, and MEDLINE. Qualifying primary research studies included human participants in US populations that were published in English between January 1, 2007, and April 30, 2019. Included articles analyzed the associations between air pollutants or heat and obstetrical outcomes. Comparative observational cohort studies and cross-sectional studies with comparators were included, without minimum sample size. Additional articles found through reference review were also considered. Articles analyzing other obstetrical outcomes, non-US populations, and reviews were excluded. Two reviewers independently determined study eligibility. The Arskey and O'Malley scoping review framework was used. Data extraction was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

FINDINGS

Of the 1851 articles identified, 68 met the inclusion criteria. Overall, 32 798 152 births were analyzed, with a mean (SD) of 565 485 (783 278) births per study. A total of 57 studies (48 of 58 [84%] on air pollutants; 9 of 10 [90%] on heat) showed a significant association of air pollutant and heat exposure with birth outcomes. Positive associations were found across all US geographic regions. Exposure to PM2.5 or ozone was associated with increased risk of preterm birth in 19 of 24 studies (79%) and low birth weight in 25 of 29 studies (86%). The subpopulations at highest risk were persons with asthma and minority groups, especially black mothers. Accurate comparisons of risk were limited by differences in study design, exposure measurement, population demographics, and seasonality.

CONCLUSIONS AND RELEVANCE

This review suggests that increasingly common environmental exposures exacerbated by climate change are significantly associated with serious adverse pregnancy outcomes across the US.

Invited Commentary: The Disillusionment of Developmental Origins of Health and Disease (DOHaD) Epidemiology

The developmental origins of health and disease (DOHaD) model promises a greater understanding of early development but has left unresolved the balance of risks and benefits to offspring of medication use during pregnancy. Masarwa et al. (Am J Epidemiol. 2018;187(8):1817-1827) conducted a meta-analysis of the association between in utero acetaminophen exposure and risks of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). A challenge of meta-analyzing results from observational studies is that summary measures of risk do not correspond to well-defined interventions when the individual studies adjusted for different covariate sets, which was the case here. This challenge limits the usefulness of observational meta-analyses for inferences about etiology and treatment planning. With that limitation understood, Masarwa et al. reported a 20%-30% higher risk of ADHD and ASD following prenatal acetaminophen exposure. Surprisingly, most of the original studies did not report diagnoses of ADHD or ASD. As a result, their summary estimates of risk are not informative about children's likelihood of ADHD and ASD diagnoses. The long-term promise of DOHaD remains hopeful, but more effort is needed in the short-term to critically evaluate observational studies suggesting risks associated with medications used to treat conditions during pregnancy that might have adverse consequences for a developing fetus.

Impacts of air pollution and noise on risk of preterm birth and stillbirth in London

BACKGROUND

Evidence for associations between ambient air pollution and preterm birth and stillbirth is inconsistent. Road traffic produces both air pollutants and noise, but few studies have examined these co-exposures together and none to date with all-cause or cause-specific stillbirths.

OBJECTIVES

To analyse the relationship between long-term exposure to air pollution and noise at address level during pregnancy and risk of preterm birth and stillbirth.

METHODS

The study population comprised 581,774 live and still births in the Greater London area, 2006-2010. Outcomes were preterm birth (<37 completed weeks gestation), all-cause stillbirth and cause-specific stillbirth. Exposures during pregnancy to particulate matter with diameter <2.5 μm (PM2.5) and <10 μm (PM10), ozone (O3), primary traffic air pollutants (nitrogen dioxide, nitrogen oxides, PM2.5 from traffic exhaust and traffic non-exhaust), and road traffic noise were estimated based on maternal address at birth.

RESULTS

An interquartile range increase in O3 exposure was associated with elevated risk of preterm birth (OR 1.15 95% CI: 1.11, 1.18, for both Trimester 1 and 2), all-cause stillbirth (Trimester 1 OR 1.17 95% CI: 1.07, 1.27; Trimester 2 OR 1.20 95% CI: 1.09, 1.32) and asphyxia-related stillbirth (Trimester 1 OR 1.22 95% CI: 1.01, 1.49). Odds ratios with the other air pollutant exposures examined were null or <1, except for primary traffic non-exhaust related PM2.5, which was associated with 3% increased odds of preterm birth (Trimester 1) and 7% increased odds stillbirth (Trimester 1 and 2) when adjusted for O3. Elevated risk of preterm birth was associated with increasing road traffic noise, but only after adjustment for certain air pollutant exposures.

DISCUSSION

Our findings suggest that exposure to higher levels of O3 and primary traffic non-exhaust related PM2.5 during pregnancy may increase risk of preterm birth and stillbirth; and a possible relationship between long-term traffic-related noise and risk of preterm birth. These findings extend and strengthen the evidence base for important public health impacts of ambient ozone, particulate matter and noise in early life.

Combined effects of traffic air pollution and home environmental factors on preterm birth in China

BACKGROUND

Although mounting evidence have linked traffic-related air pollution (TRAP) with increased risk of preterm birth (PTB), whether it can interact with indoor environmental factors remains unknown, and its window(s) susceptibility at the stage of gestation is unclear.

OBJECTIVE

To explore PTB risk for prenatal exposure to traffic-related air pollution and home environmental factors during pregnancy, so as to identify critical window(s) in the combined effect of traffic air pollution and main home environmental factor(s) on PTB development.

METHODS

A retrospective cohort study of 3,509 preschool children was performed in Changsha, China during 2011-2012. The PTB prevalence was reported by the parents based on a questionnaire. We estimated each mother's exposure to traffic-related air pollutant NO₂ in different windows of gestation, including conception month, three trimesters, birth month, and whole gestation. Maternal exposure to home environmental factors was considered by renovation (new furniture/redecoration) in pregnancy, and mold/damp stains and window condensation during perinatal period. Associations of PTB with both ambient NO₂ and home environmental factors, and their interactions on PTB were evaluated by logistic regression models using odds ratio (OR) with 95% confidence interval (CI).

RESULTS

Traffic air pollutant NO₂ exposure in utero was significantly associated with PTB, with adjusted odds ratio (OR) (95% CI) of 1.41 (1.00-1.98) for an IQR increase in NO₂ exposure during whole pregnancy, particularly in the conception month and 1^st trimester. We further found a positive relationship between perinatal exposure to mold/damp stains in the homes and PTB, OR (95% CI) = 1.73 (1.04-2.90). Especially, we detected a significant interaction between outdoor NO₂ and indoor mold/damp stains on PTB risk. Male and female foetus were respectively more susceptible to perinatal mold/dampness at home and outdoor NO₂ exposure in early gestation.

CONCLUSION

Our finding indicates that both outdoor traffic air pollutant and indoor mold/dampness play key roles in PTB development, and their interaction effect in early pregnancy significantly increases PTB risk.

Ethnic Enclaves and Pregnancy and Behavior Outcomes Among Asian/Pacific Islanders in the USA

OBJECTIVES

Ethnic enclaves are ethnically, spatially, and socially distinct communities that may promote health through access to culturally appropriate resources and reduced exposure to discrimination. This study examined ethnic enclave residence and pregnancy outcomes among Asian/Pacific Islander (API) women in the USA.

DESIGN

We examined 9206 API births in the Consortium on Safe Labor (2002-2008). Ethnic enclaves were defined as hospital regions with high percentage of API residents (> 4%), high dissimilarity index (> 0.41; distribution of API and white residents within a geographic area), and high isolation index (> 0.03; interaction between API and white residents in an area). Gestational diabetes mellitus (GDM), preterm birth (PTB), small for gestational age (SGA), and smoking and alcohol use during pregnancy were reported in medical records supplemented with ICD-9 codes. Hierarchical logistic regression models estimated associations between ethnic enclaves and pregnancy outcomes, adjusted for maternal factors, area-level poverty, and air pollution.

RESULTS

Women in enclaves had lower odds of GDM (OR 0.61; 95%CI 0.45, 0.82), PTB (OR 0.74; 95%CI 0.56, 0.99), and SGA (OR 0.68; 95%CI 0.52, 0.89) compared with women in non-enclaves. Prenatal smoking and alcohol use appeared less likely in enclaves, but estimates were imprecise. Within enclaves, about 10.5% of homes speak an API language, compared with 6.0% in non-enclaves. The mean percent of foreign-born API populations was 67.4% in enclaves and 68.8% in non-enclaves.

CONCLUSIONS

API women residing in ethnic enclaves had better pregnancy outcomes than API women residing in non-enclave areas. Access to culturally appropriate social supports and resources may be important for health promotion among API populations.

Associations between PM2.5 and risk of preterm birth among liveborn infants

PURPOSE

Studies suggest exposure to ambient particulate matter less than 2.5 μg/m3 in aerodynamic diameter (PM2.5) may be associated with preterm birth (PTB), but few have evaluated how this is modified by ambient temperature. We investigated the relationship between PM2.5 exposure during pregnancy and PTB in infants without birth defects (1999-2006) and enrolled in the National Birth Defects Prevention Study and how it is modified by concurrent temperature.

METHODS

PTB was defined as spontaneous or iatrogenic delivery before 37 weeks. Exposure was assigned using inverse distance weighting with up to four monitors within 50 kilometers of maternal residence. To account for state-level variations, a Bayesian two-level hierarchal model was developed.

RESULTS

PTB was associated with PM2.5 during the third and fourth months of pregnancy (range: (odds ratio (95% confidence interval) = 1.00 (0.35, 2.15) to 1.49 (0.82, 2.68) and 1.31 (0.56, 2.91) to 1.62 (0.7, 3.32), respectively); no week of exposure conveyed greater risk. Temperature may modify this relationship; higher local average temperatures during pregnancy yielded stronger positive relationships between PM2.5 and PTB compared to nonstratified results.

CONCLUSIONS

Results add to literature on associations between PM2.5 and PTB, underscoring the importance of considering co-exposures when estimating effects of PM2.5 exposure during pregnancy.

Air Pollution and Preterm Birth: Do Air Pollution Changes over Time Influence Risk in Consecutive Pregnancies among Low-Risk Women?

Since the 2000s, air pollution has generally continued to decrease in the U.S. To investigate preterm birth (PTB) risk associated with air pollutants in two consecutive pregnancies, we estimated exposures using modified Community Multiscale Air Quality models linked to the NICHD Consecutive Pregnancy Study. Electronic medical records for delivery admissions were available for 50,005 women with singleton births in 20 Utah-based hospitals between 2002–2010. We categorized whole pregnancy average exposures as high (>75th percentile), moderate (25–75) and low (<25). Modified Poisson regression estimated second pregnancy PTB risk associated with persistent high and moderate exposure, and increasing or decreasing exposure, compared to persistent low exposure. Analyses were adjusted for prior PTB, interpregnancy interval and demographic and clinical characteristics. Second pregnancy PTB risk was increased when exposure stayed high for sulfur dioxide (32%), ozone (17%), nitrogen oxides (24%), nitrogen dioxide (43%), carbon monoxide (31%) and for particles < 10 microns (29%) versus consistently low exposure. PTB risk tended to increase to a lesser extent for repeated PTB (19–21%) than for women without a prior PTB (22–79%) when exposure increased or stayed high. Area-level changes in air pollution exposure appear to have important consequences in consecutive pregnancies with increasing exposure associated with higher risk.

Acute air pollution exposure and NICU admission: a case-crossover analysis

PURPOSE

Neonatal intensive care unit (NICU) admission rates have increased over time. Air pollution is associated with adverse pregnancy outcomes, but the relationship between prenatal air pollution exposure and NICU admission has not been investigated.

METHODS

In the Consortium on Safe Labor (2002-2008), 27,189 singletons were admitted to the NICU. Modified Community Multiscale Air Quality models estimated exposures for criteria air pollutants and constituents of particles less than or equal to 2.5 microns (PM_2.5). Case-crossover analyses calculated odds ratios and 95% confidence intervals for interquartile range increases in pollutant exposure, comparing exposures during the week of delivery to control periods before and after delivery.

RESULTS

In models that adjusted for PM_2.5, exposure to PM_2.5 constituents during the week before delivery was significantly associated with increased odds of NICU admission: elemental carbon (35%), ammonium ions (37%), nitrate compounds (16%), organic compounds (147%), and sulfate compounds (35%). Odds were also significantly increased by day of and day before delivery exposures to carbon monoxide (4%-5%), nitrogen dioxide (13%), nitrogen oxides (4%-8%), particles less than or equal to 10 microns (2%), particles less than or equal to 2.5 microns (2%), and sulfur dioxide (3%-6%). No associations were observed for ozone.

CONCLUSIONS

Acute exposures to PM_2.5 constituents and several traffic-related pollutants during the week before delivery, the day of delivery, and day before delivery appear to increase the odds of NICU admissions. These novel associations suggest infants exposed in utero to common air pollutants may require additional care during the newborn hospital admission.

Impacts of gestational age uncertainty in estimating associations between preterm birth and ambient air pollution

Supplemental Digital Content is available in the text.

Background:

Previous epidemiologic studies utilizing birth records have shown heterogeneous associations between air pollution exposure during pregnancy and the risk of preterm birth (PTB, gestational age <37 weeks). Uncertainty in gestational age at birth may contribute to this heterogeneity.

Methods:

We first examined disagreement between clinical and last menstrual period-based (LMP) determination of PTB from individual-level birth certificate data for the 20-county Atlanta metropolitan area during 2002 to 2006. We then estimated associations between five trimester-averaged pollutant exposures and PTB, defined using various methods based on the clinical or LMP gestational age. Finally, using a multiple imputation approach, we incorporated uncertainty in gestational age to quantify the impact of this variability on associations between pollutant exposures and PTB.

Results:

Odds ratios (OR) were most elevated when a more stringent definition of PTB was used. For example, defining PTB only when LMP and clinical diagnoses agree yielded an OR of 1.09 (95% confidence interval [CI] = 1.04, 1.14) per interquartile range increase in first trimester carbon monoxide exposure versus an OR of 1.04 (95% CI = 1.01, 1.08) when PTB was defined as either an LMP or clinical diagnosis. Accounting for outcome uncertainty resulted in wider CIs—between 7.4% and 43.8% wider than those assuming the PTB outcome is without error.

Conclusions:

Despite discrepancies in PTB derived using either the clinical or LMP gestational age estimates, our analyses demonstrated robust positive associations between PTB and ambient air pollution exposures even when gestational age uncertainty is present.

Air pollution exposure during pregnancy: maternal asthma and neonatal respiratory outcomes

PURPOSE

Maternal asthma increases adverse neonatal respiratory outcomes, and pollution may further increase risk. Air quality in relation to neonatal respiratory health has not been studied.

METHODS

Transient tachypnea of the newborn (TTN), asphyxia, and respiratory distress syndrome (RDS) were identified using medical records among 223,375 singletons from the Consortium on Safe Labor (2002-2008). Community Multiscale Air Quality models estimated pollutant exposures. Multipollutant Poisson regression models calculated adjusted relative risks of outcomes for interquartile range increases in average exposure. Maternal asthma and preterm delivery were evaluated as effect modifiers.

RESULTS

TTN risk increased after particulate matter (PM) less than or equal to 10-micron exposure during preconception and trimester one (9-10%), and whole-pregnancy exposure to PM less than or equal to 2.5 microns (PM2.5; 17%) and carbon monoxide (CO; 10%). Asphyxia risk increased after exposure to PM2.5 in trimester one (48%) and whole pregnancy (84%), CO in trimester two and whole pregnancy (28-32%), and consistently for ozone (34%-73%). RDS risk was associated with increased concentrations of nitrogen oxides (33%-42%) and ozone (9%-21%) during all pregnancy windows. Inverse associations were observed with several pollutants, particularly sulfur dioxide. No interaction with maternal asthma was observed. Restriction to term births yielded similar results.

CONCLUSIONS

Several pollutants appear to increase neonatal respiratory outcome risks.

Using electronic health record data for environmental and place based population health research: a systematic review

PURPOSE

We conducted a systematic review of literature published on January 2000-May 2017 that spatially linked electronic health record (EHR) data with environmental information for population health research.

METHODS

We abstracted information on the environmental and health outcome variables and the methods and data sources used.

RESULTS

The automated search yielded 669 articles; 128 articles are included in the full review. The number of articles increased by publication year; the majority (80%) were from the United States, and the mean sample size was approximately 160,000. Most articles used cross-sectional (44%) or longitudinal (40%) designs. Common outcomes were health care utilization (32%), cardiometabolic conditions/obesity (23%), and asthma/respiratory conditions (10%). Common environmental variables were sociodemographic measures (42%), proximity to medical facilities (15%), and built environment and land use (13%). The most common spatial identifiers were administrative units (59%), such as census tracts. Residential addresses were also commonly used to assign point locations, or to calculate distances or buffer areas.

CONCLUSIONS

Future research should include more detailed descriptions of methods used to geocode addresses, focus on a broader array of health outcomes, and describe linkage methods. Studies should also explore using longitudinal residential address histories to evaluate associations between time-varying environmental variables and health outcomes.

Recent Approaches to Estimate Associations Between Source-Specific Air Pollution and Health

PURPOSE OF REVIEW

Estimating health effects associated with source-specific exposure is important for better understanding how pollution impacts health and for developing policies to better protect public health. Although epidemiologic studies of sources can be informative, these studies are challenging to conduct because source-specific exposures (e.g., particulate matter from vehicles) often are not directly observed and must be estimated. We reviewed recent studies that estimated associations between pollution sources and health to identify methodological developments designed to address important challenges.

RECENT FINDINGS

Notable advances in epidemiologic studies of sources include approaches for (1) propagating uncertainty in source estimation into health effect estimates, (2) assessing regional and seasonal variability in emissions sources and source-specific health effects, and (3) addressing potential confounding in estimated health effects. Novel methodological approaches to address challenges in studies of pollution sources, particularly evaluation of source-specific health effects, are important for determining how source-specific exposure impacts health.

Advances in environmental and occupational disorders in 2016

In this review we highlight recent studies that advance the knowledge and understanding of the effects of various environmental factors and associated immune responses in patients with allergic diseases. This review will focus on new literature regarding allergic and immune responses to a variety of environmental factors, including aeroallergens, stinging insects, fungi, pollutants, viral respiratory tract infections, climate change, and microbial exposures.

Decomposition Analysis of Black-White Disparities in Birth Outcomes: The Relative Contribution of Air Pollution and Social Factors in California

BACKGROUND

Racial/ethnic disparities in preterm birth (PTB) are well documented in the epidemiological literature, but little is known about the relative contribution of different social and environmental determinants of such disparities in birth outcome. Furthermore, increased focus has recently turned toward modifiable aspects of the environment, including physical characteristics, such as neighborhood air pollution, to reduce disparities in birth outcomes.

OBJECTIVES

To apply decomposition methods to understand disparities in preterm birth (PTB) prevalence between births of non-Hispanic black individuals and births of non-Hispanic white individuals in California, according to individual demographics, neighborhood socioeconomic environment, and neighborhood air pollution.

METHODS

We used all live singleton births in California spanning 2005 to 2010 and estimated PTBs and other adverse birth outcomes for infants borne by non-Hispanic black mothers and white mothers. To compare individual-level, neighborhood-level, and air pollution [Particulate Matter, 2.5 micrometers or less (PM_2.5) and nitrogen dioxide (NO₂)] predictors, we conducted a nonlinear extension of the Blinder-Oaxaca method to decompose racial/ethnic disparities in PTB.

RESULTS

The predicted differences in probability of PTB between black and white infants was 0.056 (95% CI: 0.054, 0.058). All included predictors explained 37.8% of the black-white disparity. Overall, individual (17.5% for PTB) and neighborhood-level variables (16.1% for PTB) explained a greater proportion of the black-white difference in birth outcomes than air pollution (5.7% for PTB).

CONCLUSIONS

Our results suggest that, although the role of individual and neighborhood factors remains prevailing in explaining black-white differences in birth outcomes, the individual contribution of PM_2.5 is comparable in magnitude to any single individual- or neighborhood-level factor. https://doi.org/10.1289/EHP490.

Asthma Outcomes and Management During Pregnancy

Asthma during pregnancy poses a common, increasingly prevalent threat to the health of women and their children. The present article reviews recent insights gained from the epidemiology of asthma during pregnancy, demonstrating the many short- and long-term risks to mother and fetus incurred by poorly controlled maternal asthma. We further discuss emerging evidence that active management of asthma during pregnancy can positively influence and perhaps completely mitigate these poor outcomes. Recent high-quality trials examining best methods for asthma treatment are reviewed and synthesized to offer an evidence-based pathway for comprehensive treatment of asthma in the outpatient setting. Safe and effective medications, as well as nonpharmacologic interventions, for asthma during pregnancy are discussed, and treatment options for related conditions of pregnancy, including depression, rhinitis, and gastroesophageal reflux, are presented. Throughout, we emphasize that an effective treatment strategy relies on a detailed patient evaluation, patient education, objective measurement of asthma control, and frequent and supportive follow-up. The cardiovascular and respiratory physiology of pregnancy is reviewed, as well as its implications for the management of patients with asthma, including patients requiring intubation and mechanical ventilation. For the situation when outpatient asthma management has failed, an approach to the critically ill pregnant patient with status asthmaticus is detailed. Multidisciplinary teams that include pulmonary specialists, obstetricians, primary care providers, nurses, pharmacists, and asthma educators improve the care of pregnant women with asthma.

Chronic and Acute Ozone Exposure in the Week Prior to Delivery Is Associated with the Risk of Stillbirth

Chronic and acute air pollution has been studied in relation to stillbirth with inconsistent findings. We examined stillbirth risk in a retrospective cohort of 223,375 singleton deliveries from 12 clinical sites across the United States. Average criteria air pollutant exposure was calculated using modified Community Multiscale Air Quality models for the day of delivery and each of the seven days prior, whole pregnancy, and first trimester. Poisson regression models using generalized estimating equations estimated the relative risk (RR) of stillbirth and 95% confidence intervals (CI) in relation to an interquartile range increase in pollutant with adjustment for temperature, clinical, and demographic factors. Ozone (O₃) was associated with a 13–22% increased risk of stillbirth on days 2, 3, and 5–7 prior to delivery in single pollutant models, and these findings persisted in multi-pollutant models for days 5 (RR = 1.22, CI = 1.07–1.38) and 6 (RR = 1.18, CI = 1.04–1.33). Whole pregnancy and first trimester O₃ increased risk 18–39% in single pollutant models. Maternal asthma increased stillbirth risk associated with chronic PM_2.5 and carbon monoxide exposures. Both chronic and acute O₃ exposure consistently increased stillbirth risk, while the role of other pollutants varied. Approximately 8000 stillbirths per year in the US may be attributable to O₃ exposure.

In vivo immune signatures of healthy human pregnancy: Inherently inflammatory or anti-inflammatory?

Changes in maternal innate immunity during healthy human pregnancy are not well understood. Whether basal immune status in vivo is largely unaffected by pregnancy, is constitutively biased towards an inflammatory phenotype (transiently enhancing host defense) or exhibits anti-inflammatory bias (reducing potential responsiveness to the fetus) is unclear. Here, in a longitudinal study of healthy women who gave birth to healthy infants following uncomplicated pregnancies within the Canadian Healthy Infant Longitudinal Development (CHILD) cohort, we test the hypothesis that a progressively altered bias in resting innate immune status develops. Women were examined during pregnancy and again, one and/or three years postpartum. Most pro-inflammatory cytokine expression, including CCL2, CXCL10, IL-18 and TNFα, was reduced in vivo during pregnancy (20-57%, p<0.0001). Anti-inflammatory biomarkers (sTNF-RI, sTNF-RII, and IL-1Ra) were elevated by ~50-100% (p<0.0001). Systemic IL-10 levels were unaltered during vs. post-pregnancy. Kinetic studies demonstrate that while decreased pro-inflammatory biomarker expression (CCL2, CXCL10, IL-18, and TNFα) was constant, anti-inflammatory expression increased progressively with increasing gestational age (p<0.0001). We conclude that healthy resting maternal immune status is characterized by an increasingly pronounced bias towards a systemic anti-inflammatory innate phenotype during the last two trimesters of pregnancy. This is resolved by one year postpartum in the absence of repeat pregnancy. The findings provide enhanced understanding of immunological changes that occur in vivo during healthy human pregnancy.

The Influence of Asthma and/or Hay Fever on Pregnancy: Data from the 1995 National Survey of Family Growth

BACKGROUND

Asthma is associated with adverse pregnancy outcomes. At the same time there is a worldwide increase in asthma and hay fever.

OBJECTIVE

This study addresses whether asthma and/or hay fever adversely influence pregnancy outcomes.

METHODS

Data from the 1995 National Survey of Family Growth that include a history of diagnosed asthma, hay fever, and adverse pregnancy outcomes in 10,847 women representative of the US population aged 15 to 44 years were analyzed.

RESULTS

Women with the allergic phenotypes asthma and hay fever and hay fever only had no significant increase in adverse pregnancy outcomes (spontaneous pregnancy loss, preterm birth, infant low birth weight), whereas women with the nonatopic phenotype asthma only (without hay fever) did. The study did not evaluate endotypes.

CONCLUSIONS

This study provides new data that the allergic phenotypes, asthma and hay fever and hay fever only, are compatible with healthy pregnancy, whereas the nonatopic asthma phenotype, asthma only, adversely impacts pregnancy.

Environmental chemicals and preterm birth: Biological mechanisms and the state of the science

PURPOSE OF REVIEW

Preterm birth is a significant worldwide health problem of uncertain origins. The extant body of literature examining environmental contaminant exposures in relation to preterm birth is extensive but results remain ambiguous for most organic pollutants, metals and metalloids, and air pollutants. In the present review we examine recent epidemiologic studies investigating these associations, and identify recent advances and the state of the science. Additionally, we highlight biological mechanisms of action in the pathway between chemical exposures and preterm birth, including inflammation, oxidative stress, and endocrine disruption, that deserve more attention in this context.

RECENT FINDINGS

Important advances have been made in the study of the environment and preterm birth, particularly in regard to exposure assessment methods, exploration of effect modification by co-morbidities and exposures, and in identification of windows of vulnerability during gestation. There is strong evidence for an association between maternal exposure to some persistent pesticides, lead, and fine particulate matter, but data on other contaminants is sparse and only suggestive trends can be noted with the current data.

SUMMARY

Beyond replicating current findings, further work must be done to improve understanding of mechanisms underlying the associations observed between environmental chemical exposures and preterm birth. By examining windows of vulnerability, disaggregating preterm birth by phenotypes, and measuring biomarkers of mechanistic pathways in these epidemiologic studies we can improve our ability to detect associations with exposure, provide additional evidence for causality in an observational setting, and identify opportunities for intervention.

Ambient Temperature and Early Delivery of Singleton Pregnancies

BACKGROUND

Extreme temperature is associated with adverse birth outcomes but it is unclear whether it increases early delivery risk.

OBJECTIVES

We aimed to determine the association between ambient temperature and early delivery.

METHODS

Medical records from 223,375 singleton deliveries from 12 U.S. sites were linked to local ambient temperature. Exposure to hot (> 90th percentile) or cold (< 10th percentile) using site-specific and window-specific temperature distributions were defined for 3-months preconception, 7-week periods during the first two trimesters, 1 week preceding delivery, and whole pregnancy. Poisson regression with generalized estimating equations calculated the relative risk (RR) and 95% confidence interval for early deliveries associated with hot/cold exposures, adjusting for conception month, humidity, site, sex, maternal demographics, parity, insurance, prepregnancy body mass index, pregnancy complications, and smoking or drinking during pregnancy. Acute temperature associations were estimated separately for warm (May-September) and cold season (October-April) in a case-crossover analysis using conditional logistic regression.

RESULTS

Compared with mild temperature (10-90th percentile), exposure to hot or cold during weeks 1-7 increased risk for early preterm (< 34 weeks) [RRhot: 1.11 (95% CI: 1.01, 1.21); RRcold: 1.20 (95% CI: 1.11, 1.30)], late preterm (34-36 weeks) [RRcold: 1.09 (95% CI: 1.04, 1.15)], and early term (37-38 weeks) [RRhot: 1.04 (95% CI: 1.02, 1.07); RRcold: 1.03 (95% CI: 1.00, 1.05)] delivery. Findings were similar for hot exposures during weeks 15-21. Examining deliveries at each week from 23 through 38, whole-pregnancy hot exposures increased delivery risk by 6-21% at weeks 34 and 36-38. In the case-crossover analysis, a 5°F increase during the week preceding delivery was associated with 12-16% higher and 4-5% lower early delivery risk during warm and cold season, respectively.

CONCLUSIONS

Both acute and chronic ambient temperature extremes may affect early delivery risk. Citation: Ha S, Liu D, Zhu Y, Kim SS, Sherman S, Mendola P. 2017. Ambient temperature and early delivery of singleton pregnancies. Environ Health Perspect 125:453-459; http://dx.doi.org/10.1289/EHP97.

Air pollution during pregnancy and lung development in the child

Air pollution exposure has increased extensively in recent years and there is considerable evidence that exposure to particulate matter can lead to adverse respiratory outcomes. The health impacts of exposure to air pollution during the prenatal period is especially concerning as it can impair organogenesis and organ development, which can lead to long-term complications. Exposure to air pollution during pregnancy affects respiratory health in different ways. Lung development might be impaired by air pollution indirectly by causing lower birth weight, premature birth or disturbed development of the immune system. Exposure to air pollution during pregnancy has also been linked to decreased lung function in infancy and childhood, increased respiratory symptoms, and the development of childhood asthma. In addition, impaired lung development contributes to infant mortality. The mechanisms of how prenatal air pollution affects the lungs are not fully understood, but likely involve interplay of environmental and epigenetic effects. The current epidemiological evidence on the effect of air pollution during pregnancy on lung function and children's respiratory health is summarized in this review. While evidence for the adverse effects of prenatal air pollution on lung development and health continue to mount, rigorous actions must be taken to reduce air pollution exposure and thus long-term respiratory morbidity and mortality.