Two commonly used antibiotics OK during pregnancy

Azithromycin and clarithromycin, commonly used in place of penicillin for allergic patients, were found not to be associated with birth defects.

By Stephen Feller

MONTREAL, Oct. 30 (UPI) -- Researchers found that two of the most commonly used antibiotics -- azithromycin and clarithromycin -- are safe for women to take during pregnancy.

Both drugs belong to a group of antibiotics called macrolides, which include in their molecular structure a macrocyclic lactone ring with one or more sugars attached. Antibiotics from this family of drugs often are used in place of drugs such as penicillin if patients are allergic to them.


The study was mounted because of a long-standing debate on the threat to health and development antibiotics may pose to pregnant women and fetuses.

"With penicillin, macrolides are amongst the most used medications in the general population and in pregnancy. However, debate remained on whether it is the infections or in fact the macrolides used to treat them that put women and their unborn child at greater risk of adverse pregnancy outcomes, including birth defects," said Dr. Anick Bérard, a researcher at the of the University of Montreal, in a press release. "We therefore aimed to estimate the risk of major congenital malformations after fetal exposure to the two most commonly used macrolides, and failed to find any."


Using data from the Quebec Pregnancy Cohort collected between 1998 and 2008, researchers analyzed data on 135,869 pregnancies, 1.7 percent of which involved a pregnant woman taking macrolides in the first trimester -- 914 were exposed to azithromycin, 734 to erythromycin, 686 to clarithromycin, and 9106 to penicillin.

Although 9.8 percent of the pregnancies resulted in a child born with a major congenital malformation, the researchers found "no meaningful association" between groups of women who gave birth to children with malformations and those who were treated with antibiotics during their pregnancies.

While researchers note that confusion over causes of defects exists -- azithromycin is used to treat chlamydia infections, but the infections themselves are associated with birth defects -- they said further studies will need to done to confirm the results of this one and to test the safety of other less-prescribed antibiotics.

The study is published in Pharmacoepidemiology and Drug Safety.

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