Use of macrolide antibiotics during pregnancy increases the risk for miscarriage. A large population based cohort study in the UK has assessing 104,605 children born from 1990-2016 with mothers prescribed with either one macrolide or one penicillin monotherapy during pregnancy. 82,314 children whose mothers were prescribed macrolides or penicillins before contraception – 53,735 siblings of the children in the study cohort were included as controls.

Major malformations were reported in 21.55 per 1,000 children whose mothers were prescribed macrolides during pregnancy and 17.36 per 1,000 in those whose mothers were prescribed penicillins. In comparison to penicillin, macrolide prescribing was associated with increased risk of any malformation (27.65 v 17.65 per 1000, adjusted risk ratio [ARR] 1.55, 95% CI 1.19 to 2.03), particularly cardiovascular malformations (10.60 v 6.61 per 1000, ARR 1.62, 95% CI 1.05 to 2.51) during the first trimester and increased risk of genital malformations (4.75 v 3.07 per 1000, ARR 1.58, 95% CI 1.14 to 2.19) in any trimester. While other system specific malformations were not significantly associated with macrolide prescribing during pregnancy, these results demonstrate that macrolide antibiotics should be used with caution in this setting. The full details of the study, published in the BMJ, can be accessed here. 

Contributed by Australian Medication Safety Services Associate – Isabella Singh