Pregnant women may want to think twice before their next trip to the taqueria, according to a study published in the monthly research journal, “Environmental Health Perspectives.”

The study—authored by Stacey A. Missmer of the Department of Epidemiology at the Harvard School of Public Health and a team of researchers here and in Texas—correlates the over-consumption of corn tortillas with neural-tube defects (NTDs) in unborn children. Often debilitating and sometimes fatal, NTDs such as anencephaly and spina bifida have been linked directly to the tortillas and other corn products in the diets of expectant mothers living along the Rio Grande.

Missmer and her associates isolated fumonsin, a fungal toxin often found in American corn crops, as the likely cause of these infants’ cranial and spinal malformations.

The study, conducted on mothers of babies born from the early 1990s to 2000, determined that overexposure to fumonsin inhibits fetal ability to absorb folic acid, a compound known to prevent NTDs.

Co-author of the study, Lucina Suarez, who works with the Texas Department of State Health Services, said the implications of NTDs can be fatal.

“With anencephaly, the cranium fails to close. This is a very serious defect, as the brain is not enclosed in the skull,” she said.

Spina bifida, or the failure of spinal cord closure, is a more common result of NTDs than anencephaly, according to Suarez.

“Among those who survive childhood [spina bifida], a majority are affected by hydrocephalus, paralysis, and lack of bowel and bladder control,” Missmer said.

But causes of NTDs remain unclear.

“In 1971, Dr. Brian McMahon reported an outbreak of NTDs that occurred in the 1930s in New England that has still not been explained,” Missmer said.

So why the tortilla connection?

NTDs and other fumonsin-related disorders seem to have a high correlation with processed corn consumption.

The study shows that women who eat 400 grams or more of corn tortilla products per day find themselves in the greatest risk bracket for passing neural-tube defects to their offspring.

Researchers found that women with NTD-positive children ate more tortillas on average during their pregnancy than those who did not.

Suarez defended the study’s method of asking women to recall the quantity of tortillas consumed over the past year, claiming the margin of error due to inaccurate memory was approximately the same for mothers of NTD-positive children as for mothers in the control group.

When asked what effect this study might have on the consumption of its products, snack manufacturer Frito-Lay declined to comment.

Despite the alarm that the tortilla hazard might cause in those who intend one day to have children, Harvard students seem generally nonplussed.

“It’s not going to affect the way I eat,” said Laura E. Martin ’06. “They come out with a new study every week; practically everything is bad for you.”

Other students doubt the study’s credibility.

“They should check their methodology,” says Wenyi Cai ’06.

Jana S. Lepon ’08 said she finds the results troubling but agrees that they may be specious.

“Perhaps people predisposed to passing on those disorders happen to eat more tortillas,” she suggested.