Maternal Exposure to Drinking-water Chlorination By- products and Small-for-gestational-age Neonates

Abstract

Background: There is concern about possible effects of disinfection by-products on reproductive outcomes. The purpose of this study was to evaluate the association between maternal exposure to chlorination by-products and the risk of delivering a small forgestational-age (SGA) neonate. Methods: We conducted a population-based case-control study in the Québec City (Canada) area. Term newborn cases with birth weights Ͻ10th percentile (n ϭ 571) were compared with 1925 term controls with birth weights Ն10th percentile. Concentrations of trihalomethanes and haloacetic acids in the water-distribution systems of participants were monitored during the study period, and a phone interview on maternal habits was completed within 3 months after childbirth. We estimated chlorination by-products ingestion during the last trimester of pregnancy and trihalomethanes doses resulting from inhalation and dermal exposure. We evaluated associations between chlorination by-products in utero exposure and SGA by means of unconditional logistic regression with control of potential confounders. Results: When total trihalomethanes and the 5 regulated haloacetic acids concentrations were divided into quartiles, no clear doseresponse relationship was found with SGA. However, increased risk was observed when haloacetic concentrations were above the fourth quartile and when either trihalomethanes or haloacetic acids concentrations were above current water standards (adjusted ORϭ 1.5 ͓95% confidence interval ϭ 1.1-1.9͔ and 1.4 ͓1.1-1.9͔, respectively). Inhalation and dermal absorption of trihalomethanes did no