The different impacts of ambient air pollution exposure on the risks of gestational hypertension and preeclampsia in twin pregnancies.

Air pollution may raise hypertension risk, but its effects on gestational hypertension and preeclampsia in twin pregnancies are unclear. This retrospective study of 3670 twin pregnancies divided participants into three groups: gestational hypertension, preeclampsia, and no hypertension. The preeclampsia group was further split into mild and severe preeclampsia. The effects of air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃) on the risks of gestational hypertension and preeclampsia were assessed during preconception, the first and second trimesters, and the first 20 weeks using multivariate logistic regression, trend regression, and restricted cubic spline (RCS) analysis. Dual-pollutant models were used for validation. In both single-pollutant and dual-pollutant models, exposure to PM_2.5 and PM₁₀ during early pregnancy (first 20 weeks and the first trimester) showed a significant protective effect against gestational hypertension. However, no significant association was found between PM_2.5 and PM₁₀ exposure and the risk of preeclampsia or Severe preeclampsia. Further analysis revealed that SO₂, NO₂, and CO exposure during the 3 months preconception were identified as risk factors for preeclampsia. For gestational hypertension, the protective effects of SO₂ and NO₂ exposure during the 3 months preconception and the first trimester disappeared after adjusting for some pollutants, but remained protective in most cases. An association was found between O₃ exposure during the 3 months preconception and gestational hypertension risk in twin pregnancies, but not with preeclampsia or severe preeclampsia risk. Air pollutants have significantly different impacts on gestational hypertension and preeclampsia in twin pregnancies, particularly during the 3 months preconception.