Pregnant women whose children are at risk for developing asthma should avoid antibiotics when they are sick, according to a recent study.

Researchers found that 22 percent of the 103 children born to mothers who took antibiotics during pregnancy were diagnosed with asthma by age 3. In contrast, only 11 percent of the children born to mothers who didn't take antibiotics prenatally were similarly diagnosed.

Recent discussions of antibiotic use have centered on the fact that overuse has increased the number of drug-resistant germs, and decreased the effectiveness of many treatments.

"We were particularly interested in how prenatal antibiotic use affected at-risk children - those with a parent with asthma, hay fever or eczema," said study author Brittany Lapin. "The prevalence in asthma has doubled in developed countries in the last 30 years, and we're still investigating why poor and minority children are diagnosed more frequently. The message to pregnant women is to avoid antibiotics to the extent that they can, and possibly avoid asthma development in their children."

Although the study revealed that prenatal antibiotic use might be associated with the development of asthma, it did not hold true for wheezing. Wheezing, a whistling or squeaky sound in the chest when you breathe, especially when exhaling, often accompanies asthma.

"The more we know about what factors increase the probability of asthma developing, the better we can assist our pregnant patients," said allergist and study co-author Dennis Ownby. "We wouldn't recommend not giving antibiotics to a pregnant woman, but we recommend caution when symptoms are not clearly caused by a bacterial infection. Pregnant women with asthma should work with their allergist to create a healthy outcome for themselves and their children."

The findings are detailed in the Annals of Allergy, Asthma and Immunology.