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.
