Acetaminophen, a commonly used over-the-counter medication, doesn't appear to increase the risk of birth defects in babies exposed to it during their mother's first trimester of pregnancy, a new University of Utah study shows.

What's more, the findings raise the possibility that women who have an infection and fever during their first trimester and take acetaminophen could actually reduce their babies' risk of birth defects such as anencephaly, cleft lip and gastrochisis.

An ingredient found in generics and 90 name-brand products registered in the U.S., acetaminophen is the recommended drug of choice for pain and fever during pregnancy, says the study, published in the January issue of the journal Obstetrics & Gynecology .

Acetaminophen is a first-line drug since other over-the-counter medications, including naproxen, are generally considered unsafe because they can decrease a pregnant woman's amniotic fluid volume, said Cara Heuser, a maternal fetal medicine fellow at Intermountain Medical Center and the University of Utah.

But there isn't a lot of data on its use.

Few studies have been conducted to ensure the drug's safety for unborn babies, said Marcia Feldkamp, an assistant professor of pediatrics at the U.'s School of Medicine. Prior research hasn't distinguished between single-ingredient acetaminophen products, such as Tylenol, and multi-ingredient products, such as cold and flu medications.

And some of those studies have produced inconclusive results, said Feldkamp, the study's lead author. The risk of gastrochisis, for instance, a birth defect in which a baby's intestines protrude from the abdomen, was reported higher in some studies but not in others.

Using data from the National Birth Defects Prevention Study, a large study from Utah and nine other states designed to investigate the genetic and environmental causes of birth defects, Feldkamp studied single-ingredient acetaminophen taken by pregnant women during their first trimester. Some 65.5 percent of pregnant women used it during pregnancy and 54.2 percent took it during the first trimester.

A total of 11,610 children exposed to acetaminophen were also studied, including 513 in Utah, and compared with a control group of 4,500 children, including 203 in Utah.

Not only was there no measurable increase in birth defects, but taking the medication actually appeared to reduce the incidence of certain problems. Feldkamp said previous research indicates an increased risk of birth defects -- in particular neural tube defects -- in babies born to women with fevers during certain critical times for development of the organs.

"Whether it's the fever or pathogen, we do not know. We cannot really distinguish that right now," she said.

Further research will have to be conducted to verify the study's findings, Feldkamp said. She also stressed pregnant women should carefully follow the directions on the package to ensure they're taking the right dosage and they should talk to their doctors.

lrosetta@sltrib.com