Relation of climatic exposures with intrahepatic cholestasis of pregnancy in a two-center retrospective cohort.

OBJECTIVE

To investigate relation between climatic exposures and intrahepatic cholestasis of pregnancy (ICP) in Chinese cities Shanghai and Sanya.

BACKGROUND

ICP is a pregnancy-specific liver disease associated with adverse fetal outcomes. Although the etiology of ICP remains unclear, climatic exposures are increasingly recognized as one of the critical correlates in ICP onset.

METHODS

This is a two-center retrospective cohort study included 48, 081 pregnant women from Shanghai (31°N, temperate) and Sanya (18°N, tropical). Baseline demographic data, pregnancy outcomes and meteorological data were collected. Generalized additive models (GAMs) were employed to analyze non-linear associations between environmental exposures and ICP risk, with statistical comparisons of baseline characteristics and complications between ICP and non-ICP groups.

RESULTS

GAM analysis revealed that temperature, sunlight and PM2.5 exhibited positive gestation-age-dependent non-linear correlations with ICP risk in Shanghai, while relative humidity showed an inverse correlation. No meteorological exposures showed significant associations with ICP in Sanya. Sunlight could amplify heat-related exposure signals alongside high temperature. In Shanghai, pregnancies conceived in February and March showed the highest ICP incidence, while Sanya showed no significant seasonal fluctuation and maintained a higher overall ICP incidence than Shanghai under constant warm climate. Thalassemia prevalence was higher in ICP cases compared to controls in both regions (Sanya: 31.8% vs. 17.9%; Shanghai:1.0% vs. 0.4%, all P<0.05). ICP patients in both cohorts demonstrated shortened gestational age, with Shanghai exhibiting a more pronounced gestational age reduction correlated with higher cesarean delivery rates.

CONCLUSION

High temperature, intense sunlight exposure, and high PM2.5 concentration across preconception and mid-pregnancy serves as major climatic correlates of ICP incidence.