A medical detective story

One of the studies presented at the annual meeting of the Society of Maternal Fetal Medicine last week was an intriguing medical detective story.

Researchers at the University of Washington in Seattle noticed that their state had a high incidence of a devastating birth defect called gastroschisis, in which organs, especially the intestines, develop outside the abdomen. The defect has a 90 percent survival rate but requires extensive interventions at and after birth.

The incidence of gastroschisis has doubled and in some places quadrupled in the past 30 years, according to the study. The researchers -- Sarah Waller, Kathleen Paul, Suzanne Peterson, and Jane Hitti, all MDs -- wondered if it might have an environmental cause.

A Washington farm

Rural areas in Washington were the hardest hit

Using the state's birth-certificate data base, they determined that the highest incidence of gastroschisis was in the agricultural eastern part of the state.  They matched cases of the defect with a history of agricultural spraying provided by the U. S. Geological Survey. Three possible culprits emerged -- atrazine, nitrates, and 2,4-dichlorophenoxyacetic acid, chemicals commonly used in agriculture.

The researchers looked at all 805 babies born with gastroschisis in Washington between 1987 and 2006 (with a control group of 3,616), and then they calculated how close the babies' mothers lived to water sources with high levels of the three chemicals.

An association between gastroschisis and atrazine, a common herbicide, emerged in the study. The closer mothers lived to a water source with high levels of atrazine, the more likely they were to have a baby with gastroschisis.

The researchers also found that the incidence of gastroschisis increased with babies conceived in the spring, when spraying is especially prevalent. No association was found with the two other chemicals.

This elegant study will be the basis of more study, no doubt, the first steps down the road toward protecting babies from a possible environmental hazard.