The four out of ten women who use antibiotics during pregnancy can breathe easy, as a comprehensive new study shows that the two most often prescribed drugs have no adverse outcome on the child’s physical development. The researchers, led by Anick Bérard of the University of Montreal and its affiliated CHU Sainte-Justine children’s hospital, and Hedvig Nordeng of the University of Oslo, looked at macrolides, a type of antibiotics. “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,” Dr. Bérard explained. “We therefore aimed to estimate the risk of major congenital malformations after foetal exposure to the two most commonly used macrolides, and failed to find any.”
The researchers referred to data held in the Quebec Pregnancy Cohort. Containing detailed medical information on hundreds of thousands of pregnancies, in addition to the outcomes for mother and newborn alike, it’s one of the world’s largest cohort of its type. Information on the mother’s use of pharmaceuticals – azithromycin and clarithromycin – was retrieved from Quebec’s public pharmaceutical insurance program and was compared to the use of penicillin, a well tolerated antibiotic. “135,839 pregnancies met the criteria for inclusion in our study. Of these, 1.7% involved exposure to the macrolides during the first trimester, while 9.8% of pregnancies resulted in the child having a major congenital malformation. After statistical analysis, we found no meaningful association between the groups compared to penicillin use,” Dr. Bérard and Professor Nordeng said.
The lack of previous clarity regarding the safety of these drugs may be due to overlooked confounding factors: for example, azithromycin is typically used to treat chlamydia infections, infections that are associated with birth defects. Nonetheless, the researchers underscore that wider studies will need to be undertaken in order to confirm the safety of less-often prescribed antibiotics.