Blood Trihalomethane Concentrations and Gestational Diabetes Mellitus: A Nationwide Cross-Sectional Study.

BACKGROUND AND

OBJECTIVE

Growing evidence suggests that environmental pollutants may increase the risk of gestational diabetes mellitus (GDM). This study aimed to assess the association between blood concentrations of trihalomethanes (THMs) and GDM, and to explore the mediating role of Homeostatic Model Assessment of β-Cell Function (HOMA-β).

METHODS

This cross-sectional study analyzed data from 2,592 participants in the National Health and Nutrition Examination Survey (NHANES, 2007-2018). Weighted multivariate logistic regression and weighted quantile sum (WQS) regression were used to evaluate the individual and combined effects of blood THMs on GDM. Mediation analysis was conducted to assess the intermediary role of HOMA-β.

RESULTS

Higher blood concentrations of chloroform (TCM), bromodichloromethane (BDCM), brominated THMs (BTHM), chlorinated THMs (CTHM), and total THMs (TTHM) were significantly associated with increased odds of GDM, with adjusted odds ratios (highest vs. lowest group) ranging from 1.58 (95% CI: 1.01-2.49) for BDCM to 2.00 (95% CI: 1.24-3.23) for CTHM. WQS analysis identified BDCM as the primary contributor to this risk. Mediation analysis revealed that HOMA-β significantly mediated 14.73%, 10.95%, 11.16%, and 10.94% of the effects of BDCM, BTHM, CTHM, and TTHM on GDM, respectively.

CONCLUSIONS

This nationally representative cross-sectional study reveals a positive association between blood THM concentrations and GDM, with BDCM as the main contributor. The association was partially mediated by reduced pancreatic β-cell function (HOMA-β). These findings suggest a potential environmental risk pathway for gestational health, warranting validation in prospective cohort studies.