TUESDAY, March 31 (HealthDay News) -- Pesticides may increase the risk of birth defects, say researchers who found that the highest rates of birth defects in U.S. babies occur among those conceived in the spring and summer, the same time that there are increased levels of pesticides in surface water.
Researchers analyzed all 30.1 million births in the United States between 1996 and 2002. They found a strong association between higher rates of birth defects among women whose last menstrual period was in April, May, June or July and elevated levels of nitrates, atrazine and other pesticides in surface water during those same months.
The data showed a statistically significant correlation between the last menstrual period and higher rates of birth defects for half of 22 categories of birth defects, including spina bifida, cleft lip, clubfoot and Down's syndrome.
"Elevated concentrations of pesticides and other agrochemicals in surface water during April through July coincided with significantly higher risk of birth defects in live births conceived by women whose last menstrual period began in the same months," study first author Dr. Paul Winchester, professor of clinical pediatrics at the Indiana University School of Medicine, said in a school news release. "While our study didn't prove a cause and effect link, the fact that birth defects and pesticides in surface water peak during the same four months makes us suspect that the two are related," he said.
It's long been believed that these chemicals pose a threat to developing embryos, but this is the first study to make the connection between birth defects and elevated levels of pesticides at the time of conception, the authors said. The study is in the April issue of the journal Acta Paediatrica.
"Birth defects, which affect about three out of 100 newborns in the U.S., are one of the leading causes of infant death. What we are most excited about is that if our suspicions are right, and pesticides are contributing to birth defect risk, we can reverse or modify the factors that are causing these lifelong and often very serious medical problems," Winchester said.
Known risk factors for birth defects include alcohol use, smoking, diabetes, and advanced age among pregnant women. But even mothers who didn't have these risk factors had higher overall birth defect rates for babies conceived from April to July, the study found.
"These observations by Dr. Winchester are extremely important, as they raise the question for the first time regarding the potential adverse effect of these commonly used chemicals on pregnancy outcome -- the health and well-being of our children," Dr. James Lemons, a professor of pediatrics at the IU School of Medicine, said in the news release.
The March of Dimes has more about birth defects.
SOURCE: Indiana University School of Medicine, news release, March 30, 2009
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