UC Irvine

Air pollution exposure has been known to increase the risk of several adverse birth outcomes, including postpartum depression (PPD) and gestational diabetes mellitus (GDM). In March 2020, the COVID-19 pandemic caused the state of California to shut down to prevent the spread of the virus. This led to changes in air pollution concentrations. Understanding how these changes influenced the association between air pollution and both PPD and GDM will provide further information into the health impacts seen during the COVID-19 pandemic period. Therefore, we sought to investigate the association between air pollution exposure and the risk of PPD and GDM. We also incorporated the impacts of experiencing the pandemic during and after pregnancy to assess whether these associations changed. Patient records from Kaiser Permanente Southern California (KPSC) electronic health records (EHRs) provided health data, socioeconomic status (SES) data, and residential address histories. Pollution data for monthly averages of particulate matter with an aerodynamic diameter ≤ 2.5 µg/m3 (PM2.5), particulate matter with an aerodynamic diameter ≤ 10 µg/m3 (PM10), nitrogen dioxide (NO2), and 8-hour ozone (O3) was spatiotemporally linked to participant residential addresses. A discrete time approach with pooled logistic regression was used for PPD models, while Cox proportional hazard models were used for GDM analyses. Subgroup analyses were performed with Cox proportional hazard models, and to investigate whether experiencing the pandemic before conception, after birth, or during pregnancy altered the associations with air pollution. We found increased risks of PPD with exposure to O3 during pregnancy and in the postpartum period; PM2.5 had significantly negative associations with PPD risk in the late pregnancy and postpartum periods. Hispanic, white, or multi-racial/other mothers, or mothers with higher incomes were more susceptible to PPD risk with ozone exposure. Positive associations between GDM risk and exposure to PM2.5, PM10, and O3 were found; no significant associations were seen with NO2 exposure, except for negative associations with second trimester exposure. Mothers with more than a college education had greater associations between GDM and exposure to all pollutants, including NO2. For PPD analyses, mothers were grouped by COVID time: not impacted (gave birth before March 2019), postpartum (gave birth between March 2019-March 2020), pregnant (pregnant in March 2020), or conceived after (date of conception after March 2020). Experiencing the COVID-19 pandemic while pregnant or in the 12-month postpartum period was positively associated with exposure to PM10 and O3. For GDM analyses, COVID time groups included: not impacted (gave birth before March 2020), pregnant (pregnant in March 2020), or conceived after (date of conception after March 2020). GDM risk was positively associated with exposure to PM2.5 for mothers who were pregnant when the pandemic began. Overall, this study shows the associations between air pollution exposure and the risk of PPD and GDM have changed since the COVID-19 outbreak. The results were different from our group’s previous studies, which found positive associations between PM exposure and PPD, and positive associations between NO2 exposure and GDM. These differences may be explained by decreases in ambient air pollution levels during the COVID-19 pandemic period, or by altered PM2.5 constituent levels. Future studies should continue to investigate the association between air pollution and maternal health during the pandemic period, especially the association with PM2.5 constituent levels.