Role of infant sex in the association between air pollution and preterm birth

Factors influencing sex ratio at birth in Krosno, Poland

The secondary sex ratio (SSR) is a widely used descriptor that reflects the living conditions and health status during pregnancy. The aim of study was to assess the impact of maternal factors, season of birth, and air pollution with the heating season on the sex ratio at birth in the Subcarpathian population from the Krosno district, Poland. A retrospective study involving 11,587 births was occurred at the John Paul II Podkarpackie Province Hospital in Krosno between 2016 and 2020. Sex of the newborn, the season of their birth, as well as the maternal age, birth order, the interval between births, and the season of birth were analysed. Furthermore, the relationship between the SSR and the level of air pollution during the heating season was investigated. To determine the significance of differences in sex ratios, chi-square analysis and multifactorial regression were used, with a significance level set at p < 0.05. At the chi-square level, all the studied factors indicated a statistically significant relationship with the SSR. However, the regression model used shows that maternal age and birth order were the most important factors in shaping the SSR in the study group.

Identifying sensitive windows of prenatal household air pollution on birth weight and infant pneumonia risk to inform future interventions

BACKGROUND

Prenatal household air pollution impairs birth weight and increases pneumonia risk however time-varying associations have not been elucidated and may have implications for the timing of public health interventions.

METHODS

The Ghana Randomized Air Pollution and Health Study (GRAPHS) enrolled 1,414 pregnant women from Kintampo, Ghana and measured personal carbon monoxide (CO) exposure four times over pregnancy. Birth weight was measured within 72-hours of birth. Fieldworkers performed weekly pneumonia surveillance and referred sick children to study physicians. The primary pneumonia outcome was one or more physician-diagnosed severe pneumonia episode in the first year of life. We employed reverse distributed lag models to examine time-varying associations between prenatal CO exposure and birth weight and infant pneumonia risk.

RESULTS

Analyses included n = 1,196 mother-infant pairs. In models adjusting for child sex; maternal age, body mass index (BMI), ethnicity and parity at enrollment; household wealth index; number of antenatal visits; and evidence of placental malaria, prenatal CO exposures from 15 to 20 weeks gestation were inversely associated with birth weight. Sex-stratified models identified a similar sensitive window in males and a window at 10-weeks gestation in females. In models adjusting for child sex, maternal age, BMI and ethnicity, household wealth index, gestational age at delivery and average postnatal child CO exposure, CO exposure during 34-39 weeks gestation were positively associated with severe pneumonia risk, especially in females.

CONCLUSIONS

Household air pollution exposures in mid- and late- gestation are associated with lower birth weight and higher pneumonia risk, respectively. These findings support the urgent need for deployment of clean fuel stove interventions beginning in early pregnancy.

Prenatal Exposure to Specific PM2.5 Chemical Constituents and Preterm Birth in China: A Nationwide Cohort Study

Exposure to fine particulate matter (PM_2.5) during pregnancy has been associated with preterm birth (PTB). However, the existing evidence is inconsistent, and the roles of specific PM_2.5 chemical constituents remain unclear. Based on the China Labor and Delivery Survey, we included birth data from 89 hospitals in 25 provinces in mainland China, and conducted a national multicenter cohort study to examine the associations of PM_2.5 and its chemical constituents with PTB risk in China. We applied satellite-based models to predict prenatal PM_2.5 mass and six main component exposure. Multilevel logistic regression analysis was used to examine the associations, controlling for sociodemographic characteristics, seasonality, and spatial variation. We observe an increased PTB risk with an increase in PM_2.5 mass and the most significant association is found during the third trimester when the adjusted odds ratio (OR) per interquartile range increases in PM_2.5 total mass is 1.12 (95% confidence Interval, CI: 1.05-1.20). Infants conceived by assisted reproductive technology (ART) show greater PTB risk associated with PM_2.5 exposure (OR = 1.33, 95% CI: 1.05-1.69) than those conceived naturally (OR = 1.11, 95% CI: 1.03-1.19). We also find black carbon, sulfate, ammonium and nitrate, often linked to fossil combustion, have comparable or larger estimates of the effect (OR = 1.07-1.14) than PM_2.5. Our findings provide evidence that components mainly from fossil fuel combustion may have a perceptible influence on increased PTB risk associated with PM_2.5 exposure in China. Additionally, compared to natural conception, conception through ART may be more susceptible to PM_2.5 exposure.

Air pollution and placental mitochondrial DNA copy number: Mechanistic insights and epidemiological challenges

During embryogenesis and embryo implantation, the copy number of mtDNA is elaborately regulated to meet the cellular demand for division, growth and differentiation. With large numbers of mitochondria for energy production, placental cells possess strong endocrine functionalities and capacities for efficient signaling communication. Recently, several environmental epidemiological studies have shown an association between mitochondrial DNA copy number, adverse birth outcomes and maternal exposure to air pollution, which has shed light on the possible effect of pollutants on placental molecular events. Because the mtDNA replication is thought to be a direct drive of mtDNA change, we tried to highlight the essential factors involved in the process of mtDNA replication. Then we traced the mtDNA change in the formation of placenta during embryogenesis, and evaluated the importance of mitochondrial genome maintenance during gestation. The possible mechanism from the epidemiological and experimental studies were reviewed and summarized, and recommendations were proposed for future studies to improve the precision of the estimated difference. The issue will be well-understood if the integrated profiles, such as familial genetic tendency, maternal genetic information, identification of mitochondrial DNA copy number in each placental cell type, and total personal exposure assessment, are considered in the future study.