Joint effects of traffic-related air pollution and hypertensive disorders of pregnancy on maternal postpartum depressive and anxiety symptoms.

Background: Ambient air pollution has been linked to postpartum depression. However, few studies have investigated the effects of traffic-related NO _x on postpartum depression and whether any pregnancy-related factors might increase susceptibility.
Objectives: To evaluate the association between traffic-related NO _x and postpartum depressive and anxiety symptoms, and effect modification by pregnancy-related hypertension.
Methods: This study included 453 predominantly low-income Hispanic/Latina women in the MADRES cohort. Daily traffic-related NO _x concentrations by road class were estimated using the California LINE-source dispersion model (CALINE4) at participants' residential locations and averaged across pregnancy. Postpartum depressive and anxiety symptoms were evaluated by a validated questionnaire (Postpartum Distress Measure, PDM) at 1, 3, 6 and 12 months postpartum. Multivariate linear regressions were performed to estimate the associations at each timepoint. Interaction terms were added to the linear models to assess effect modification by hypertensive disorders of pregnancy (HDPs). Repeated measurement analyses were conducted by using mixed effect models.
Results: We found prenatal traffic-related NO _x was associated with increased PDM scores. Specifically, mothers exposed to an IQR (0.22 ppb) increase in NO _x from major roads had 3.78% (95% CI: 0.53-7.14%) and 5.27% (95% CI: 0.33-10.45%) significantly higher 3-month and 12-month PDM scores, respectively. Similarly, in repeated measurement analyses, higher NO _x from major roads was associated with 3.06% (95% CI: 0.43-5.76%) significantly higher PDM scores across the first year postpartum. Effect modification by HDPs was observed: higher freeway/highway and total NO _x among mothers with HDPs were associated with significantly higher PDM scores at 12 months postpartum compared to those without HDPs.
Impact: This study shows that prenatal traffic-related air pollution was associated with postpartum depressive and anxiety symptoms. The study also found novel evidence of greater susceptibility among women with HDPs, which advances the understanding of the relationships between air pollution, maternal cardiometabolic health during pregnancy and postpartum mental health. Our study has potential implications for clinical intervention to mitigate the effects of traffic-related pollution on postpartum mental health disorders. The findings can also offer valuable insights into urban planning strategies concerning the implementation of emission control measures and the creation of green spaces.
(© 2024. The Author(s).)