Gastroschisis, a birth defect in which the intestines grow outside the body, is more common among babies conceived in the spring when the levels of the herbicide atrazine in water are highest, researchers from Indiana reported.
In Washington, women who live near water contaminated with atrazine are more likely to have a baby with gastroschisis, especially if they get pregnant in spring, a study found.
Atrazine, applied on corn crops in Wisconsin and much of the Midwest, is found in some drinking water and can be absorbed through the skin and lungs. Exposure to the chemical is the latest potential risk factor to emerge in the effort to unravel the mystery of gastroschisis, one of the most puzzling of birth defects.
Unlike most defects, gastroschisis ("gas-tro-SKI-sis") clearly is on the rise, said Russell Kirby, a birth defects statistics expert who tracks the condition.
The Centers for Disease Control and Prevention estimates 1,871 children are born with gastroschisis in the U.S. each year, or 1 in 2,229 births.
The defect is more common in babies of women who are teenagers or are thin, possibly because the mothers lack adequate nutrients to carry a pregnancy, Kirby said.
"There really isn't another birth defect where you see this kind of pattern," said Kirby, of the University of South Florida and formerly with the Wisconsin Department of Health Services.
Other risk factors suggested by research: smoking, drinking, urinary tract infections and use of common painkillers and illicit drugs.
About 90 percent of babies with gastroschisis survive today, up from about 20 percent in the 1960s, but many suffer complications. The babies require extensive care after birth, costing an average of $150,000 or more.
Austin Wells, 8, from Hermansville, a small town in Michigan's Upper Peninsula, is an example of how serious gastroschisis can be.
He spent most of his first 20 months at UW Children's Hospital, on tube feeding that destroyed his liver. At age 2, he got a new liver, pancreas and intestines through a transplant.
Today, Austin takes 20 medications, gets sick frequently and wears an ostomy bag for bowel movements.
"This is kind of worst-end gastroschisis," said his father, Matt Wells.
Despite the toll, gastroschisis receives less attention than some rarer childhood disorders such as Wilms tumor, a type of kidney cancer, said Dr. Peter Nichol, a pediatric surgeon at UW Hospital who repairs gastroschisis in newborns.
"It's a travesty," Nichol said.
In 2007, Dr. Paul Winchester of St. Francis Hospital in Indianapolis found a slight uptick of gastroschisis in Indiana among babies conceived in May and June, when atrazine levels are higher in surface water.
Another study in 2009 by Winchester showed the rate of all birth defects was 3 percent higher for babies conceived in April through July, when atrazine levels are higher. The study found an increase in 11 specific defects during those months — including gastroschisis, which occurred 4 percent more often in April through July than other months.
Though the percentage increases are small, they're significant because there are millions of births each year and gastroschisis is likely undercounted, Winchester said.
A study last year by doctors in Seattle showed a 60 percent higher incidence of gastroschisis among infants in Washington whose mothers lived within 15 miles of surface water tainted with atrazine, compared to those living more than 30 miles away.
Ann Bryan, a spokeswoman for Syngenta, which makes atrazine, said it's "the most carefully examined pesticide in the world."
More than 6,000 studies over 50 years, and the Environmental Protection Agency and World Health Organzation, "have found atrazine to be safe at levels found in the environment," she said.
Winchester said his studies and the one from Washington show an association between gastroschisis and atrazine, not proof of a cause. But he noted other research has shown trace amounts of atrazine can alter the development of frogs.
"We're seeing some very ominous trends," he said.