Getting Pregnant In Spring, Summer Linked to Birth Defects

Kathleen Blanchard's picture
Conception and Pregnancy

A new study suggests that women who get pregnant in spring or summer in the United States may be at risk for delivering infants with birth defects, which include spina bifida, cleft lip, clubfoot and Down's syndrome.

Study author Paul Winchester, M.D., Indiana University School of Medicine professor of clinical pediatrics explains, "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. 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."

The strong association between birth defects among women who conceive in spring and summer was seen when the researchers examined records of 30.1 million births in the U.S., occurring between 1996 and 2002. The scientists studied 22 categories of birth defects, and found a significant increase in half of birth defect categories, related to the last month of menses, taken from a Centers for Disease Control database from 1996 to 2002.


The scientists suggest that, in the US, elevated levels of nitrates, atrazine and other pesticides appear in surface water during the same months, making birth defects from pesticides a likely possibility when conception occurs during spring or summer.

One in three hundred children in the US are born with birth defects. The researchers point out that most of the chemicals in surface water in the US during spring and summer are banned in Europe, in particular, atrazine. The study also found that even without other risk factors, such as diabetes, smoking and pregnancy in women who were older, spring and summer conception still correlated with the number of birth defects seen among the women.

The good news is, if the study results are true, there is much that can be done. Dr. Winchester says, “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."

The observations from the study are published in the April medical journal Acta Pædiatrica. Though there has been no definite cause established between surface water contamination and birth defects, the study is the first to show a link between birth defects and getting pregnant in spring and summer, when increased levels of pesticides are present in surface water across the United States.

Reference: Indiana University