RALEIGH, N.C. (The News & Observer) -- It has long been known that the behavior and environment of the mother during pregnancy can affect a newborn's health.

But new research suggests that a father's behavior is important, too.

Scientists at the University of North Carolina-Chapel Hill have found that different parental occupations may bring increased risk of birth defects.

For example, photographers seem to have a greater risk of having a child with eye defects. The children of landscapers have a greater risk for gastrointestinal defects.

Yet Tania Desrosiers, an epidemiologist at University of North Carolina's Gillings School of Global Public Health and the lead author of the study, cautioned that the heightened risks are still small.

"Dads shouldn't worry or change jobs," she said.

Birth defects are rare conditions. For example, only 1 in about 700 births results in a baby with a heart defect. Still, birth defects are the leading cause of infant mortality, and those who live with defects struggle.

The causes of about 70 percent of birth defects are still unknown.

The university scientists looked at more than 60 different jobs and 60 different defects, using data from 10,000 pregnancies with defects (not all pregnancies made it to term) and 4,000 live births without defects. The paper was published in Occupational and Environmental Medicine.

Although the study establishes a correlation between jobs and defects, it does not establish the cause.

It could be that DNA in the father's sperm is damaged by chemical or radiation exposure. A chemical could be carried on a sperm into the uterus, or there could be "take-home exposure," such as pesticide residue on clothes, Desrosiers said.

"If you suspect you work with toxic chemicals, use personal protective equipment, which you should be using anyway," she said.

Different occupations have exposure to different chemicals. Janitors are around cleaning products, and photographers are exposed to developing solvents. Drivers are near diesel fumes, while landscapers are around pesticides.

But chemical exposure may not be the whole story. Some surprising jobs, such as mathematicians and computer scientists, had elevated risks for certain defects. Desrosiers said the simple act of sitting might raise the temperature in the genitals and cause changes in sperm.

No matter what the cause of the defects, the implication of the study is clear.

"Dads do play a role in the health of their unborn child," Desrosiers said. "The next set of studies will try to figure out why."

(c)2012 The News & Observer (Raleigh, N.C.) Distributed by McClatchy-Tribune News Service.