About 19,000 fetal deaths occur in the United States each year, and the causes remain a significant public health problem. Among known risk factors are smoking, advanced age among pregnant women and previous history of fetal deaths.

In the past, few epidemiological studies of pesticide exposure and birth defects have considered timing of possible exposures. And now it appears pregnant women living close to farms where pesticides are sprayed on fields may have an increased risk of having a fetus die due to birth defects.

This is the first study to our knowledge of pesticides and pregnancy in which exposures were in close proximity to the subjects and the verification of pesticide use was objective, not relying on people's memories of what they might have been exposed to.

Researchers found a slight increase of fetal death due to birth defects when pesticides were applied near where the pregnant women lived.

That span -- much of the first trimester -- appears to be a special window of vulnerability for birth defects, just as earlier research has suggested. If the women were exposed during the 3rd and 8th week of pregnancy -- the point when the fetal organs are forming -- the fetus seemed to be the most vulnerable to the effects of pesticide exposure.

The association increased for women living within 1 square mile of the field where pesticide application occurred.

The take home message is clear:

Living close to areas where agricultural pesticides are applied will boost the risk of fetal death due to birth defects.

Epidemiology March 2001;22:148-156