A Canadian study has identified an increased risk of miscarriage with the use of five common classes of antibiotics in early pregnancy.
The research, published in the Canadian Medical Association Journal (CMAJ), found the use of macrolides (excluding erythromycin), quinolones, tetracyclines, sulfonamides and metronidazole during early pregnancy was associated with an increased risk of spontaneous abortion. Nitrofurantoin exposure was not associated with an increased risk of miscarriage, which supports its use as an alternative to trimethoprim-sulfamethoxazole for the treatment of urinary tract infections during pregnancy.
Azithromycin and metronidazole were associated with a 65 per cent and 70 per cent increased risk of miscarriage respectively, while sulphonamides, tetracyclines, quinolones and clarithromycin more than doubled the risk. Results were similar regardless of whether penicillins or cephalosporins were used as comparators.
“Although antibiotic use to treat infections has been linked to a decreased risk of prematurity and low birth weight in other studies, our investigation shows that certain types of antibiotics are increasing the risk of spontaneous abortion, with a 60 per cent to two-fold increased risk,” explained senior author, Dr. Anick Bérard. “Nevertheless, the increased risk was not seen for all antibiotics, which is reassuring for users, prescribers, and policy-makers,” she added.