Prenatal Exposure to Air Pollution and Pre-Labor Rupture of Membranes in a Prospective Cohort Study: The Role of Maternal Hemoglobin and Iron Supplementation

Association of household air pollution exposure and anemia among pregnant women: Analysis of baseline data from 'Household Air Pollution Intervention Network (HAPIN)' trial

BACKGROUND

Anemia is common in low- and middle-income countries (LMICs), causing significant health issues and social burdens. Exposure to household air pollution from using biomass fuels for cooking and heating has been associated with anemia, but the exposure-response association has not been studied.

OBJECTIVES

We evaluated the associations between personal exposure to air pollution and both hemoglobin levels and anemia prevalence among pregnant women in a multi-country randomized controlled trial.

METHODS

We studied 3,163 pregnant women aged 18-35 years with 9-20 weeks of gestation, recruited as part of the Household Air Pollution Intervention Network (HAPIN) randomized controlled trial in Guatemala, India, Peru, and Rwanda. We assessed 24-hour personal exposures to fine particulate matter (PM2.5), black carbon (BC), and carbon monoxide (CO), and measured hemoglobin levels at baseline (15 ± 3 weeks gestation). Linear and logistic regression models were used to examine the associations of measured pollutants with hemoglobin levels and anemia prevalence, adjusting for confounding.

RESULTS

Single-pollutant models showed associations of CO with higher hemoglobin levels and lower anemia prevalence. Bipollutant models involving CO and PM2.5 also revealed that an interquartile range (IQR) increase in CO concentrations (2.26 ppm) was associated with higher hemoglobin levels [β = 0.04; 95 % confidence interval (CI): 0.01, 0.07], and a lower odds of anemia prevalence [odds ratios (OR) = 0.90; 95 % CI: 0.83, 0.98]. PM2.5 was inversely related to hemoglobin and positively associated with anemia, but results were not statistically significant at the 0.05 alpha level. County-specific results showed that 3 of 4 countries showed a similar association between CO and hemoglobin. We found no association of BC levels with hemoglobin levels or with anemia prevalence.

CONCLUSION

Our findings suggest that exposure to CO is associated with higher hemoglobin and lower anemia prevalence among pregnant women, whereas PM2.5 showed the opposite associations.

Maternal Exposure to Environmental Air Pollution and Premature Rupture of Membranes: Evidence from Southern China

BACKGROUND Exposure to air pollution (AP) during pregnancy is associated with pre-labor rupture of membranes (PROM). However, there is limited research on this topic, and the sensitive exposure windows remain unclear. The present study assessed the association between AP exposure and the risk of PROM, as well as seeking to identify the sensitive time windows. MATERIAL AND METHODS This retrospective study analyzed 4276 pregnant women's data from Tongling Maternal and Child Health Hospital from 2020 to 2022. We obtained air pollution data, including particulate matter (PM) with an aerodynamic diameter of ≤2.5 μm (PM₂․₅), particulate matter with an aerodynamic diameter of ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), and ozone (O₃), from the Tongling Ecology and Environment Bureau. Demographic information was extracted from medical records. We employed a distributed lag model to identify the sensitive exposure windows of prenatal AP affecting the risk of PROM. We conducted a sensitivity analysis based on pre-pregnancy BMI. RESULTS We found a significant association between prenatal exposure to AP and increased PROM risk after adjusting for confounders, and the critical exposure windows of AP were the 6th to 7th months of pregnancy. In the underweight group, an increase of 10 µg/m³ in PM₂․₅ was associated with a risk of PROM, with an odds ratio (OR) of 1.48 (95% CI: 1.16, 1.89). Similarly, a 10 µg/m³ increase in PM₁₀ was associated with a risk of PROM, with an OR of 1.45 (95% CI: 1.05, 1.77). CONCLUSIONS Prenatal exposure to AP, particularly during months 6-7 of pregnancy, is associated with an increased risk of PROM. This study extends and strengthens the evidence on the association between prenatal exposure to AP and the risk of PROM, specifically identifying the critical exposure windows.

The relationship between maternal exposure to ambient air pollutants and premature rupture of membranes: A systematic review and meta-analysis

Air pollution is an environmental stimulus that may predispose pregnant women to preterm rapture of membrane (PROM). However, the relationship of maternal exposure to air pollutants and PROM is still unclear. To investigate the relationship between the long-term and short-term maternal exposure to air pollution and PROM. We searched all studies published in PubMed, Embase and Web of Science up to February 2024. The studies provided quantitative effect estimates with 95% confidence intervals, for the impact of short-term (<30 days) or long-term (≥30 days) maternal exposure to air pollutants on PROM, preterm PROM (PPROM) or term PROM (TPROM). The odds ratio (OR), risk ratio (RR), or hazard ratio (HR), with 95% confidence intervals was extracted, and RR or HR were deemed as OR because of the low prevalence of PROM. Fixed- or random-effects meta-analyses performed. In total, 17 relevant studies were included. Maternal exposure to PM2.5 in the second trimester increases the risk of PROM (pooled OR = 1.15, 95%CI: 1.05-1.26). Maternal exposure to PM10, NO2, NO, CO and SO2 during pregnancy and short-term maternal exposure to PM2.5, NO2, SO2 and O3 also associate with PROM occurrence. The results of the study show that both long-term maternal exposure in the second or third trimester and short-term maternal exposure to ambient air pollution can increase the risk of PROM.

Exposure to air pollution as a risk factor for anaemia: a global scoping review

Anaemia is an important global health issue with various factors responsible for its occurrence. Though nutritional deficiency is one of the main causes of the disease, evidence suggests a potential link between long-term exposure to ambient air pollution and an increased risk of developing anaemia. Our scoping review evaluates studies conducted across the world to examine possible associations between anaemia and ambient air pollution. Six databases were searched, 153 sources were identified, and 21 articles were included in the review. Apart from one article which showed no significant effect, studies reported positive associations between anaemia and air pollution. This was true for both indoor and outdoor air pollution, various types of particulate matter exposure, and across demographic groups. The review highlights the importance of recognizing exposure to air pollution as a potential risk factor for anaemia and emphasizes the imperative for focused interventions and policy measures to mitigate air pollution.

Ambient air pollution and the dynamic transitions of stroke and dementia: a population-based cohort study

Background

Stroke and dementia are the leading causes of neurological disease burden. Detrimental effects of air pollution on both conditions are increasingly recognised, while the impacts on the dynamic transitions have not yet been explored, and whether critical time intervals exist is unknown.

Methods

This prospective study was conducted based on the UK Biobank. Annual average air pollution concentrations at baseline year 2010 estimated by land-use regression models were used as a proxy for long-term air pollution exposure. Associations between multiple air pollutants (PM2.5, PM2.5-10, and NO2) indicated by air pollution score and the dynamic transitions of stroke and dementia were estimated, and the impacts during critical time intervals were explored. The date cutoff of this study was February 29, 2020.

Findings

During a median follow-up of 10.9 years in 413,372 participants, 6484, 3813, and 376 participants developed incident stroke, dementia, and comorbidity of stroke and dementia. For the overall transition from stroke to comorbid dementia, the hazard ratio (HR) for each interquartile range (IQR) increase in air pollution score was 1.38 (95% CI, 1.15, 1.65), and the risks were limited to two time intervals (within 1 year and over 5 years after stroke). As for the transition from dementia to comorbid stroke, increased risk was only observed during 2-3 years after dementia.

Interpretation

Our findings suggested that air pollution played an important role in the dynamic transition of stroke and dementia even at concentrations below the current criteria. The findings provided new evidence for alleviating the disease burden of neurological disorders related to air pollution during critical time intervals.

Funding

The State Scholarship Fund of China Scholarship Council.

Prenatal air pollution, fetal β-cell dysfunction and neurodevelopmental delay

BACKGROUND

Emerging evidence has reported significant associations of prenatal air pollution exposure with neurodevelopmental delay in offspring. Sensitive exposure windows and the modifiable factor remain elusive.

OBJECTIVE

We aim to identify sensitive windows of air pollution during pregnancy on neurodevelopmental delay, and examine whether cord blood C-peptide mediates the relationship.

METHODS

This study included 7438 mother-newborn pairs in Hefei, China, from 2015 to 2021. Weekly exposure to particulate matter of aerodynamic diameter <2.5 µm, 10 µm (PM2.5, PM10), nitrogen dioxide (NO2) and carbon monoxide (CO) was estimated at regulatory air monitoring stations in Hefei. Denver Developmental Screening Test-II and the Gesell Developmental Schedules were applied to assess the neurodevelopmental delay in children 6-36 mon of age. Distributed lag nonlinear models examined sensitive time windows of prenatal air pollutants exposure. Mediation analysis estimated the mediating role of cord blood C-peptide.

RESULTS

The sensitive PM2.5, PM10, NO2, and CO exposure windows associated with neurodevelopmental delay were throughout pregnancy. Weekly air pollutants exposure was related to higher neurodevelopmental delay risks [cumulative odds ratio (OR): 1.40(1.29,1.53) in PM2.5 (per 10 μg/m3), 1.40(1.28,1.53) in PM10 (per 10 μg/m3), 1.41(1.30,1.52) in CO (per 0.1 mg/m3), and 1.49(1.29,1.72) in NO2 (per 5 μg/m3)]. Mediation analysis indicated 18.3 % contributions of cord C-peptide to the relationship [average mediation effect: 0.04(0.01.0.06); average direct effect: 0.15(0.07.0.25)].

CONCLUSIONS

Exposure to air pollution throughout pregnancy is linked to neurodevelopmental delay mediated by poorer fetal β-cell function. Screening and treatment of abnormal glucose metabolism in infants could benefit the prevention of air pollution-associated neurodevelopment delay.

Maternal exposure to ambient air pollution mixture and premature rupture of membranes: Evidence from a large cohort in Southern California (2008-2018)

BACKGROUND

There is minimal evidence of relationships between maternal air pollution exposure and spontaneous premature rupture of membranes (SPROM), a critical obstetrical problem that can significantly increase maternal and fetal mortality and morbidity. No prior study has explored the PROM risk related to specific components of particulate matter with aerodynamic diameters of ≤ 2.5 µm (PM2.5). We examined associations between maternal exposure to nitrogen dioxide (NO2), ozone (O3), PM2.5, PM10, and PM2.5 constituents and SPROM.

METHODS

A large retrospective cohort study was conducted and included 427,870 singleton live births from Kaiser Permanente Southern California during 2008-2018. Monthly averages of NO2, O3 (8-h daily maximum), PM2.5, and PM10 were measured using empirical Bayesian kriging based on measurements from monitoring stations. Data on PM2.5 sulfate, nitrate, ammonium, organic matter, and black carbon were obtained from a fine-resolution model. A discrete time approach with pooled logistic regressions was used to estimate associations throughout the pregnancy and based on trimesters and gestational months. The quantile-based g-computation models were fitted to examine the effects of 1) the air pollution mixture of four pollutants of interest and 2) the mixture of PM2.5 components.

RESULTS

There were 37,857 SPROM cases (8.8%) in our study population. We observed relationships between SPROM and maternal exposure to NO2, O3, and PM2.5. PM2.5 sulfate, nitrate, ammonium, and organic matter were associated with higher SPROM risks in the single-pollutant model. Mixture analyses demonstrated that the overall effects of the air pollution mixture and PM2.5 mixture in this study were mainly driven by O3 and PM2.5 nitrate, respectively. Underweight mothers had a significantly higher risk of SPROM associated with NO2.

CONCLUSION

Our findings add to the literature on associations between air pollution exposure and SPROM. This is the first study reporting the impact of PM2.5 constituents on SPROM.