The differential impacts of environmental air pollution exposure on the risk of placenta previa and placenta accreta in twin pregnancies.

BACKGROUND

This study aims to investigate the association between exposure to air pollutants during pregnancy (until placental accreta) in twin pregnancies and the risk of abnormal placental positioning and development.

METHODS

This retrospective study included 3,670 pregnant women with twin pregnancies, classified into three groups: no placenta previa or accreta (3,017 cases), placenta previa (119 cases), and placenta accreta without previa (534 cases). Air pollution data (PM2.5, PM10, SO2, NO2, CO, and O3) were collected from 12 monitoring stations in Chongqing. Exposure estimates were calculated using geocoding based on hospital locations and the nearest stations. Multivariate logistic regression and trend regression analyses, adjusted for confounders, assessed the impact of these pollutants on placenta previa and placenta accreta risk during the 3 months preconception, first trimester, and second trimester. Stratified analyses based on maternal characteristics and restricted cubic spline (RCS) analysis were performed. A dual-pollutant model was used to validate the results.

RESULTS

Results showed that none of the six pollutants were significantly associated with placenta previa in either single-pollutant or dual-pollutant models. In the subtypes of placenta previa, NO was found to be a protective factor for marginal placenta previa only during the 3 months preconception, with no significant associations observed for other pollutants. For placenta accreta, both single-pollutant and dual-pollutant models indicated that exposure to PM, PM, SO, and NO during the 3 months preconception might have a protective effect. In contrast, O significantly increased the risk of placenta accreta during both the 3 months preconception and the first trimester, regardless of whether it was analyzed in a single-pollutant or dual-pollutant model. Furthermore, the dual-pollutant model revealed that NO and CO were risk factors for placenta accreta during the second trimester after adjusting for PM and PM. Stratified analyses based on maternal characteristics showed stable associations between the six pollutants and placenta previa across different periods, while the impact of pollutants on placenta accreta varied under different maternal clinical characteristics.

CONCLUSION

The mechanisms by which air pollutants affect placenta previa and placenta accreta in twin pregnancies are notably different.