Perinatal & Pediatric
Acute impact of air pollution on fetal death in the San Joaquin Valley, California: a time-stratified case-crossover study Sneha Ghimire* Sneha Ghimire Alec M. Chan-Golston Asa Bradman Valerie Martinez
Background: Fetal death affects approximately 0.57% of pregnancies. Recent research suggests that air pollution may affect fetal development and mortality. The San Joaquin Valley (SJV) of California is an underserved region with a significant air pollution burden but the impacts of air pollution on fetal death in this area is unclear.
Methods: In this case-crossover study, we identified 1,343 singleton fetal deaths (>20 weeks gestation) in the SJV from 2016 to 2019. Daily zip-code level concentrations of ozone (O3) and particulate matter < 2.5 microns (PM2.5) were derived from Community Multi-scale Air Quality models by the San Joaquin Valley Air Pollution Control District and geospatially linked to the maternal zip codes at delivery. Using conditional logistic regression models, we compared exposures during case periods shortly before the event with control periods when the event did not happen, within the same mother to eliminate time-invariant confounding. Case periods were the day of the event and each of the 14 days prior (lag0-lag14). Control periods were selected using the time-stratified approach. OR and 95% CI were calculated for each 10-unit increase in exposures while adjusting for temperature and humidity.
Results: PM2.5 and O3 were positively associated with higher odds of fetal death in the cold (Nov-Apr) and warm (May-Oct) seasons, respectively. Each 10-unit increase in cold season PM2.5 and warm season O3 was associated with 5% (aORlag6 1.05, 95% CI 1.00,1.12) and 7% (aORlag6 1.07, 95% CI 1.02,1.13) increased odds of fetal death six days post-exposure, respectively. The associations appeared stronger in Asian, Hawaiian/Pacific Islander, low-income, and older mothers.
Conclusions: Air pollution may contribute to fetal death risk. In the changing climate where air pollution exposure is expected to increase in certain areas, efforts to reduce exposure in pregnant people are critical and should be strengthened, especially in underserved populations.