Diarrhea: a new risk factor for neural tube defects?

Neural tube defects (NTDs) affect approximately 4000 US pregnancies annually. Folic acid supplementation taken before conception protects against the occurrence of NTDs. Adequate levels of vitamin B12 also appear to play a significant role. Gastrointestinal disturbances, such as those caused by diarrhea, might negatively affect the availability of these vitamins, thereby increasing the risk of these birth defects.

To determine whether periconceptional diarrhea increases the risk of NTD-affected pregnancies, a population-based case-control study was conducted in the 14 Texas-Mexico border counties. Information on diarrhea and other risk factors was ascertained by in-person interview. Study subjects were Mexican-American women who resided and delivered in any border county during 1995-2000. Case women, identified through active surveillance, had liveborn or stillborn infants or fetuses diagnosed with anencephalus, spina bifida, or encephalocele. Control women were randomly selected from women delivering normal live births in study area health facilities.

One or more episodes of periconceptional diarrhea were associated with increased risk of NTD-affected pregnancies compared to no episodes of diarrhea (OR = 3.7, 95% CI = 1.8-7.6). This association was independent of fever, obesity, maternal age, maternal birthplace, income, prior unproductive pregnancy, and dietary plus multivitamin folate intake, known risk factors for NTDs.

Confirmation of this new risk factor might have public health implications due to the feasibility of modifying exposure.