Use of macrolides during pregnancy and risk of birth defects: results of the population study

According to several studies, the use of macrolides during pregnancy can lead to birth defects, but this type of information is very heterogeneous.

Until 2005, macrolides were considered safe for use during pregnancy. However, in 2005, the results of a study conducted in Sweden were published, which showed that the risk of developing cardiovascular malformations in children was doubled if mothers used erythromycin during pregnancy. These results led to the fact that in Sweden and Norway, regulatory medical agencies issued a warning regarding contraindications to the use of erythromycin during the first trimester of pregnancy. However, such warnings have not been issued in the United States and Canada.

Researchers in Canada have assessed the risk of developing major birth defects after using macrolides during pregnancy, focusing on malformations of the cardiovascular system. The results were published in the October issue of Pharmacoepidemiology and drug safety.

In a population study, a cohort of pregnant patients from Quebec (Quebec Pregnancy Cohort, Canada) was used. This cohort is one of the largest cohorts of pregnant women in the world.

All women were divided into 3 groups: effects during pregnancy of macrolides, penicillins and lack of exposure. In total, the results of 135,859 pregnancies were analyzed, including 914 cases of exposure to azithromycin during the first trimester of pregnancy, 734 cases of erythromycin, 686 cases of clarithromycin and 9,105 penicillins. Significant birth defects have been recorded during the 1 year of children's lives.

About all 10 pregnancies (9.8%) ended in the birth of a child in whom a significant malformation was diagnosed at 1 year; in 1.7% of all pregnancies, macrostids in the first trimester were used.

After adjustment for potential interference factors, use of azithromycin was found to be (relative risk (RR) 1.19, 95% confidence interval 0.98-1.44, 120 cases) , erythromycin (RR 0.96, 95% CI 0.74-1.24, 66 cases) and clarithromycin (RR 1.12, 95% CI 0.99-1.42, 79 cases) during the first trimester of pregnancy did not statistically significantly increase the risk of developing serious birth defects, including CCC abnormalities.

Thus, the results of this cohort study have shown that the use of any macrolide during the first trimester of pregnancy does not entail an increased risk of serious malformations, in general, and malformations of the cardiovascular system, in particular.