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

Clinical analysis of 126 cases of stillbirth in high-altitude areas

OBJECTIVE

This study aims to analyze the clinical characteristics of stillbirths in high-altitude areas, strengthen monitoring of high-risk pregnant women, improve maternal health care levels, and reduce perinatal mortality rates.

METHODS

A retrospective collection of 126 cases of stillbirth in Nyingchi People's Hospital from 2015 to 2021 was divided into an pre-stage group (2015-2019,87 cases) and a post-stage group (2020-2021,39 cases). The incidence of stillbirth and clinical characteristics were compared between the two groups. The cases were classified into maternal factors, fetal factors, placenta/membrane/umbilical cord factors, and unknown causes, and the clinical characteristics and possible etiologies of different gestational ages and antenatal examination situations were analyzed.

RESULT

The overall incidence of stillbirth in the high-altitude area of this study was 2.36%, with2.07% in the pre-stage group and 3.43% in the post-stage group. There were significant differences between the two groups in gestational age and antenatal examination situation (P = 0.003 and 0.008). The main causes of stillbirth were maternal factors (45.28%), followed by placenta/membrane and umbilical cord factors (28.30%), unknown causes (17.61%), and fetal factors (8.81%). The main causes of stillbirth include hypertensive disorder complicating pregnancy, premature rupture of membranes, severe anemia, and fetal malformatiohypertensive disorder complicating pregnancyns.

CONCLUSION

This study provides new insights into the prevention and management of stillbirths in high-altitude areas, particularly in terms of maternal factors such as gestational hypertension and severe anemia, by analyzing the clinical characteristics and influencing factors of 126 cases of stillbirths in high-altitude areas. Therefore, this study suggests strengthening prenatal and antenatal health care management to reduce the risk of stillbirth, improve pregnancy outcomes, and promote maternal and child health.

Environmental pollutant SO₂ exposure affects trophoblast function involving an ER stress pathway

Sulphur dioxide (SO₂) is a toxic air pollutant with deleterious effects on the respiratory, cardiovascular, endocrine and reproductive systems. SO₂, being freely diffusible, can cross the placenta and reach the fetal system. Previous studies have reported the association between SO₂ exposure and adverse pregnancy and fetal outcomes without much emphasis on its molecular aspects. The present study has investigated the adverse consequences of SO₂ derivatives on the two key trophoblast functions critical for placentation: invasion and fusion. SO₂ exposure inhibited the fusogenic potential of BeWo cells, as well as the invasion and migratory ability of the extravillous HTR8/SVneo cells. A molecular insight revealed dysregulated endoplasmic reticulum stress, with an altered epigenetic state as seen by histone modifications following SO₂ exposure. Collectively, our findings revealed the harmful effect of SO₂ and its consequences on the placental function. We therefore elucidated the detrimental impact of SO₂ exposure on trophoblast cells and the possible health consequences that may contribute to pregnancy-related complications as a result of compromised placental function. KEY POINTS: Sulphur dioxide (SO₂) derivatives severely impaired trophoblasts migration, invasion and its ability of fusogenic differentiation. SO₂ derivatives appear to affect trophoblast cell interactions, thereby affecting its 3D organization and its capacity to form spheroids. Mechanistic insight into these events indicates SO₂ derivatives mediated the induction of endoplasmic reticulum stress and inflammation, as well as altered histone-3 markers. We therefore conclude that SO₂ exposure has a detrimental effect on placental trophoblast cells. Long-term exposure during pregnancy may result in an adverse outcome.

A case-crossover study of air pollution exposure during pregnancy and the risk of stillbirth in Tehran, Iran

The growing fetus is very sensitive to environmental conditions. There is limited and conflicting evidence about the short-term effects of exposure to air pollutants on the pregnancy outcome. In this time-stratified case-crossover study, the effect of several air pollutants (i.e. O3, CO, NO2, SO2, and PM2.5) on the occurrence of stillbirth was evaluated in Tehran (the capital of Iran) between December 2018 and March 2023. Using a quasi-Poisson regression model and distributed lag nonlinear models (DLNM), we estimated the effect of exposure to air pollutants measured as lags (0 to 7 days) and cumulative average days (0-2, 0-6, and 0-14-day lag) before delivery on stillbirth. The association was adjusted for potential confounding factors including meteorological factors. During the study period in Tehran, 5311 stillbirths were reported. In single-pollutant models, during the entire year, SO2 (lag 1 day) and NO2 (lag 2 days) were found to have a direct and significant relationship with stillbirth. In the warm seasons, we found direct and inverse relationships between NO2 (lag 2 days) and PM2.5 (lag 4 days), respectively. In cold seasons, PM 2.5 (lag 1 day) and cumulative lag (0-2 days), SO2 (lag 1 day), and cumulative lag (0-2 and 0-6 days) were found to have direct and significant relationships with stillbirth. In two-pollutant models, SO2 & CO, and SO2 & O3, direct and significant associations were observed between SO2 exposures and stillbirth for the entire year. A similar pattern was observed for PM2.5 in combinations with NO2, and O3 and for NO2 in the two-pollutant model (O3 & NO2). However, in warm seasons, inverse associations were observed between PM2.5 and stillbirth in combinations with O3, NO2, and SO2, while NO2 showed a direct association in combinations with PM2.5, CO, and O3. In the cold seasons, direct and significant associations were observed between SO2 and stillbirth in model combinations with CO, O3, and NO2. This relationship was observed for PM2.5 in combination with CO, and NO2. Also, for CO in the two-pollutant model of CO & NO2. As a result, this study showed evidence of a relationship between short-term exposure to ambient air pollution before birth, especially SO2, NO2, PM2.5, and CO with increased risk of stillbirth.

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.

Prenatal exposure to fine particulate matter chemical constituents and the risk of stillbirth and the mediating role of pregnancy complications: A cohort study

Evidence on the association of fine particulate matter (PM2.5) exposure with stillbirth is limited and inconsistent, which is largely attributed to differences in PM2.5 constituents. Studies have found that the hazards of certain PM2.5 constituents to the fetus are comparable to or even higher than total PM2.5 mass. However, few studies have linked PM2.5 constituents to stillbirth. Moreover, the mediating role of pregnancy complications in PM2.5-related stillbirth remains unclear. To our knowledge, this study was the first to explore the individual and mixed associations of PM2.5 and its constituents with stillbirth in China. After matching the concentrations of PM2.5 and its constituents (sulfate [SO42-], nitrate [NO3-], ammonium [NH4+], organic matter [OM], and black carbon [BC]) for participants according to their geographical location, there were 170,507 participants included in this study. We found that stillbirth was associated with exposure to PM2.5 and its constituents in the year before pregnancy and during the entire pregnancy, and the associations in trimester 1 were strongest. The risk of stillbirth increased sharply when PM2.5 and its constituents during pregnancy exceeded the median concentrations. Moreover, stillbirth was associated with exposure to the mixtures of SO42-, NO3-, NH4+, OM, and BC before and during pregnancy (trimesters 1 and 2). Meanwhile, two-pollutant models also suggested stillbirth was associated with PM2.5 and its constituents in the year before and during pregnancy. The associations of PM2.5 and its constituents with stillbirth were stronger in mothers with advanced age and without cesarean delivery history. Additionally, hypertensive disorders in pregnancy, gestational diabetes, and placental abruption mediated the association of PM2.5 with stillbirth. Therefore, enhanced protection against PM2.5 for pregnant women before and during pregnancy and targeted interventions for pregnancy complications and anthropogenic sources of PM2.5 constituents are important to reduce stillbirth risk.

A retrospective study of air quality associated with teratogenic pathogen screening in women of reproductive age in southern China

Adverse pregnancy outcomes are associated with a poor ambient atmospheric environment. Infections by teratogenic pathogens such as cytomegalovirus (CMV) and herpes simplex virus (HSV) are the main cause of the worse pregnant outcomes. However, environmental factors governing these infections are uncertain and epidemiological studies are limited. An epidemiological study on relationships between air pollutants and antibodies against teratogenic pathogens will be explored. In total, 5475 women of childbearing age were enrolled in the study between January 2018 and December 2019 in a hospital in Shantou, China. Antibodies against pathogens were measured by electrochemical luminescence. Everyday air quality data, concerning particulate matter (PM), sulfur dioxide (SO2), nitrogen dioxide (NO2), and other parameters, were acquired from a government web site, and the relationships between them were evaluated with nonparametric and multivariate linear regression analyses. Not only titers of herpes simplex virus HSV(I+II) IgGs in spring, but also titers of cytomegalovirus IgG (CMV IgG) and HSV I IgG in autumn, both had positive associations with concentrations of SO2. When PM2.5 or PM10 exposure is elevated, HSV(I+II) IgGs, TOX IgM should be paid more attention in spring or summer. Air pollution may be crucial for teratogenic pathogen infections. This study highlights air pollution could increase the risk of teratogenic pathogen infection, implying stronger measures should be taken to protect air environment and screenings of associated antibody should be strengthened in different season.