Pregnancy Outcome After Gestational Exposure to Erythromycin - a Population-based Register Study from Norway

Aims: Erythromycin is a macrolide antibiotic indicated for respiratory tract infections, genital chlamydia and skin infections. It has recently been suggested that erythromycin use in the first trimester of pregnancy can increase the risk of congenital cardiovascular malformations. This study aimed to determine whether erythromycin exposure in the first trimester is associated with cardiovascular or other malformations.

Methods: We studied 180 120 women in Norway who were pregnant during 2004-2007. Data on all live births stillbirths and induced abortions after 12 gestational weeks from The Medical Birth Registry of Norway (MBRN) were linked to information from the Norwegian prescription database (NorPD). We compared the pregnancy outcomes of women who had taken erythromycin (n= 1786, 1.0%), penicillin V (n= 4921, 2.7%) or amoxicillin (n= 1599, 0.9%) in their first trimester with outcomes of women who had not taken any systemic antibiotics (n= 163 653, 90.9%) during this period.

Results: The risk of cardiovascular malformations was not significantly different with or without exposure to erythromycin in the first trimester (adjusted OR = 1.2 [95% CI 0.8, 1.8]) or in the most vulnerable period of heart formation (adjusted OR = 1.6 [95% CI 0.9-3.0]). Sub-analyses showed that the risk for any specific malformations was not increased with erythromycin, macrolides, penicillin V or amoxicillin compared with no antibiotic use in first trimester.

Conclusions: This large, population-based register study did not find that exposure to erythromycin or macrolides in the first trimester of pregnancy was associated with fetal cardiovascular or other malformations. These results suggest that the risk of erythromycin use during early pregnancy, if any, is low.