31 March 2009

Season of conception linked to birth defect risk

by Kate Melville

Birth defect rates in the United States are highest for women conceiving in the spring and summer - the time when pesticide levels in surface water across the country reach their peak.

Writing in the medical journal Acta P�diatrica, the researchers explain how they reached their conclusions by analyzing all 30.1 million births that occurred between 1996 and 2002. During this period, the researchers found a strong association between the increased number of birth defects in children of women whose last menstrual period occurred in April, May, June or July and elevated levels of nitrates, atrazine and other pesticides in surface water during the same months.

"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," said Indiana University's Paul Winchester, the first author of the study. "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."

Birth defects are known to be associated with risk factors such as alcohol, smoking, diabetes or advanced age. Significantly, however, the researchers found that even mothers who didn't report these risk factors had higher overall birth defect rates for babies conceived from April to July.

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Source: Indiana University