Higher daily nitrate intake from drinking water during pregnancy associated with birth defects

Jean Brender Ph.D.

Jean Brender Ph.D.

Findings from a study of mothers and their exposures during the first trimester of pregnancy suggest that higher nitrate intake from drinking water sources might be associated with some types of defects in babies. Published recently in Environmental Health Perspectives, the study took place in Iowa and Texas. The investigators used data from participants of the National Birth Defects Prevention Study and linked mothers’ addresses to their drinking water sources and respective nitrate content. They also accounted for reported use of bottled water.

“What we found is that women who gave birth to babies with some types of birth defects tended to consume higher amounts of nitrate from drinking water on a daily basis than women who gave birth to babies without major birth defects,” said study author Jean Brender, Ph.D., R.N., associate dean for research and professor at the Texas A&M Health Science Center School of Rural Public Health.  Daily intake of nitrate from drinking water was estimated from nitrate content in drinking water sources and from reported amounts of water consumed during the first trimester.

The study found that:

•    Mothers of babies with spina bifida were twice as likely as mothers of babies without major birth defects to ingest 5 mg or more of nitrate daily from drinking water versus less than 0.91 mg.
•    Mothers of babies with limb deficiencies, cleft palate, and cleft lip were, respectively, 1.8, 1.9 and 1.8 times more likely than mothers of babies without major birth defects to ingest 5.42 mg or more of nitrate daily versus one mg or less of nitrate.

Private well water in agricultural areas would likely have the highest levels of nitrate, authors said. “Expectant mothers who get their drinking water from private wells should get their water tested for nitrate,” said study co-author Pete Weyer, Ph.D., associate director of the University of Iowa Center for Health Effects of Environmental Contamination. “Municipal water supplies are tested on a regular basis, but private wells are not.”  In Iowa, private well water can be tested at no cost to the well owner; testing is done through county health departments. In other states the test costs about $20.

More information about the study:

With data from the National Birth Defects Prevention Study, researchers linked addresses of 3,300 case-mothers (who delivered babies with major birth defects) and 1,121 control-mothers (who delivered babies without major birth defects) from the Iowa and Texas sites to public water supplies and respective nitrate measurements. They assigned nitrate levels for bottled water from collection of representative samples and standard laboratory testing. Nitrate levels in drinking water of private well users were estimated through complex modeling of environmental conditions (Texas only). Daily nitrate consumption was estimated from self-reported water consumption at home and work.

Previous studies of prenatal exposure to drinking water nitrate and birth defects in offspring have not accounted for water consumption patterns or potential interaction with nitrosatable drugs.  (Many common drugs, such as some antihistamines, antibiotics, and decongestants are nitrosatable, and past studies have suggested that interactions of nitrosatable drugs with nitrite might increase risk for some types of birth defects). In the present study, higher daily intake of nitrate from drinking water did not strengthen associations between prenatal use of nitrosatable drugs and birth defects in babies.

Co-authors of the study included Paul A. Romitti, Binayak P. Mohanty, Mayura U. Shinde, Ann M. Vuong, Joseph R. Sharkey, Dipankar Dwivedi, Scott A. Horel, Jiji Kantamneni, John C. Huber Jr., Qi Zheng, Martha M. Werler, Katherine E. Kelley, John S. Griesenbeck, F. Benjamin Zhan, Peter H. Langlois, Lucina Suarez, and Mark A. Canfield.

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