Air Pollution and Risk of Placental Abruption: A Study of Births in New York City, 2008-2014

Modeling the human placenta: in vitro applications in developmental and reproductive toxicology

During its temporary tenure, the placenta has extensive and specialized functions that are critical for pre- and post-natal development. The consequences of chemical exposure in utero can have profound effects on the structure and function of pregnancy-associated tissues and the life-long health of the birthing person and their offspring. However, the toxicological importance and critical functions of the placenta to embryonic and fetal development and maturation have been understudied. This narrative will review early placental development in humans and highlight some in vitro models currently in use that are or can be applied to better understand placental processes underlying developmental toxicity due to in utero environmental exposures.

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.

"We adjusted for race": now what? A systematic review of utilization and reporting of race in American Journal of Epidemiology and Epidemiology, 2020-2021

Race is a social construct, commonly used in epidemiologic research to adjust for confounding. However, adjustment of race may mask racial disparities, thereby perpetuating structural racism. We conducted a systematic review of articles published in Epidemiology and American Journal of Epidemiology between 2020 and 2021 to (1) understand how race, ethnicity, and similar social constructs were operationalized, used, and reported; and (2) characterize good and poor practices of utilization and reporting of race data on the basis of the extent to which they reveal or mask systemic racism. Original research articles were considered for full review and data extraction if race data were used in the study analysis. We extracted how race was categorized, used-as a descriptor, confounder, or for effect measure modification (EMM)-and reported if the authors discussed racial disparities and systemic bias-related mechanisms responsible for perpetuating the disparities. Of the 561 articles, 299 had race data available and 192 (34.2%) used race data in analyses. Among the 160 US-based studies, 81 different racial categorizations were used. Race was most often used as a confounder (52%), followed by effect measure modifier (33%), and descriptive variable (12%). Fewer than 1 in 4 articles (22.9%) exhibited good practices (EMM along with discussing disparities and mechanisms), 63.5% of the articles exhibited poor practices (confounding only or not discussing mechanisms), and 13.5% were considered neither poor nor good practices. We discuss implications and provide 13 recommendations for operationalization, utilization, and reporting of race in epidemiologic and public health research.

Air pollution and pregnancy

Increased fossil fuel usage and extreme climate change events have led to global increases in greenhouse gases and particulate matter with 99% of the world's population now breathing polluted air that exceeds the World Health Organization's recommended limits. Pregnant women and neonates with exposure to high levels of air pollutants are at increased risk of adverse health outcomes such as maternal hypertensive disorders, postpartum depression, placental abruption, low birth weight, preterm birth, infant mortality, and adverse lung and respiratory effects. While the exact mechanism by which air pollution exerts adverse health effects is unknown, oxidative stress as well as epigenetic and immune mechanisms are thought to play roles. Comprehensive, global efforts are urgently required to tackle the health challenges posed by air pollution through policies and action for reducing air pollution as well as finding ways to protect the health of vulnerable populations in the face of increasing air pollution.

The impact of household fuel usage on adverse pregnancy outcomes in rural Ma'anshan City, Anhui Province: a birth cohort study

The combustion of cooking fuels generates detrimental gases significantly impacting human health, particularly for vulnerable populations like expectant mothers. Prenatal exposure of such hazardous emissions raises the probability of adverse pregnancy outcomes, including preterm birth (PTB) and low birth weight (LBW). Our research aims to explore the association between cooking fuel utilization and adverse birth outcomes in rural Ma'anshan, Anhui Province. A prospective cohort study was executed, employing the Maternal and Infant Health Assessment questionnaire to classify fuels into clean (natural gas, electricity) and polluting energy sources (coal, coal gas, firewood). Multivariate logistic regression models were conducted to evaluate the association between fuel consumption and postpartum maternal and infant outcomes. Among the 442 surveyed pregnant women, 38.2% (N=169) utilized polluting fuels. After adjusting for covariates such as age and BMI, the relative risks of preterm birth, low birth weight, and postpartum hemorrhage in the polluting fuel group compared to the clean fuel group were OR: 3.27, 95% CI: 1.34, 8.00; OR: 3.50, 95% CI: 1.12, 10.90; and OR: 3.18, 95% CI: 1.06, 9.46, respectively. These results indicate that the usage of polluting fuels during pregnancy may heighten the risk of adverse birth outcomes. Consequently, additional research is advised to mitigate the harmful emissions generated by cooking fuels and advocate for clean energy adoption, enhancing maternal and infant well-being.

Bias Amplification and Variance Inflation in Distributed Lag Models Using Low-Spatial-Resolution Data

Distributed lag models (DLMs) are often used to estimate lagged associations and identify critical exposure windows. In a simulation study of prenatal nitrogen dioxide (NO2) exposure and birth weight, we demonstrate that bias amplification and variance inflation can manifest under certain combinations of DLM estimation approaches and time-trend adjustment methods when using low-spatial-resolution exposures with extended lags. Our simulations showed that when using high-spatial-resolution exposure data, any time-trend adjustment method produced low bias and nominal coverage for the distributed lag estimator. When using either low- or no-spatial-resolution exposures, bias due to time trends was amplified for all adjustment methods. Variance inflation was higher in low- or no-spatial-resolution DLMs when using a long-term spline to adjust for seasonality and long-term trends due to concurvity between a distributed lag function and secular function of time. NO2-birth weight analyses in a Massachusetts-based cohort showed that associations were negative for exposures experienced in gestational weeks 15-30 when using high-spatial-resolution DLMs; however, associations were null and positive for DLMs with low- and no-spatial-resolution exposures, respectively, which is likely due to bias amplification. DLM analyses should jointly consider the spatial resolution of exposure data and the parameterizations of the time trend adjustment and lag constraints.

Ambient PM2.5 exposure and salivary cortisol output during pregnancy in a multi-ethnic urban sample

OBJECTIVES

Evidence from murine research supports that fine particulate matter (PM2.5) may stimulate the hypothalamic-pituitary-adrenal axis, leading to elevated circulating glucocorticoid levels. Epidemiologic research examining parallel associations document similar associations. We examined these associations among a diverse sample of pregnant individuals exposed to lower levels of ambient PM2.5.

MATERIALS AND METHODS

Participants included pregnant individuals enrolled in the PRogramming of Intergenerational Stress Mechanisms (PRISM) pre-birth cohort. Daily residential PM2.5 exposure was estimated using a satellite-based spatial-temporal hybrid model. Maternal 3rd trimester salivary cortisol levels were used to calculate several features of the diurnal cortisol rhythm. We used multivariable linear regression to examine PM2.5 during the pre-conception period and during each trimester in relation to cortisol awakening rise (CAR), slope, and area under the curve relative to ground (AUCG).

RESULTS AND DISCUSSION

The average PM2.5 exposure level across pregnancy was 8.13 µg/m3. PM2.5 in each exposure period was positively associated with AUCG, a measure of total cortisol output across the day. We also observed an inverse association between PM2.5 in the 3rd trimester and diurnal slope, indicating a steeper decline in cortisol throughout the day with increasing exposure. We did not detect strong associations between PM2.5 and slope for the other exposure periods or between PM2.5 and CAR for any exposure period.

CONCLUSIONS

In this sample, PM2.5 exposure across the preconception and pregnancy periods was associated with increased cortisol output, even at levels below the U.S. National Ambient Air Quality Annual Standard for PM2.5 of 12.0 µg/m3.

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.