Periconceptional Exposure to Nitrates in Drinking Water and Risk for Neural Tube Defects

Abstract

Epidemiologic studies investigating associations between drinking water nitrate levels and neural tube defect (NTD)-affected pregnancies have been inconclusive. This case-control study investigated the association between drinking water nitrate levels and NTD-affected pregnancies in 43 Mexican-American case-women and 67 MexicanAmerican control-women who were living along the Texas-Mexico border and who had either NTD-affected pregnancies/births or normal births between June 1995 and May 2000. The study subjects were interviewed in person about periconceptional maternal exposures, and samples of usual drinking water during the periconceptional period were collected and measured for nitrate concentration levels. Women exposed to periconceptional drinking water nitrate concentration levels >3.52 mg/liter were more likely to have NTD-affected pregnancies, adjusted odds ratio (OR) = 1.76, 95% confidence interval (Cl) = 0.76 - 4.07. This increased association between nitrate exposure and risk for NTD was modified by body mass index (BMI). Women with BMI > 30 kg/m who were exposed to nitrate concentration levels >3.52 mg/liter had 9.4 times the risk for NTD-affected pregnancies (95% Cl: 1.02 - 98.39) compared to women with BMI < 30 kg/m who were exposed to the same nitrate levels. Further research is warranted to investigate the causal inferences suggested by these findings. The observed increased rates in this unique study population are important in terms of public health implications for the entire Texas-Mexico border region.