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Use of some common antibiotics in pregnancy linked to increased risk of miscarriage

A new Canadian study found that using certain antibiotics during pregnancy was linked to a higher risk of miscarriage. Classes of drugs associated with higher risk included quinolones, tetracyclines, sulfonamides, and macrolides (except erythromycin). 

There was no increased risk linked to the penicillin and cephalosporin drug classes. Specific antibiotics that were not associated with higher miscarriage risk included erythromycin and nitrofurantonin. 

Antibiotics are often used in pregnancy, but existing research did not provide clear guidance on the safety of different types of antibiotics, the study authors wrote. Their study included 8,702 women who had a miscarriage in Quebec between 1998 and 2009. These women were matched to 87,020 pregnancies that did not end in miscarriage. This control group was selected to match the gestational age and year of pregnancy of the women who had miscarriages. The researchers then compared antibiotic use between the two groups.

Of the women who had miscarriages, 1,428 (16.4 per cent) had been prescribed an antibiotic during pregnancy. In the control group, 11,018 (12.6 per cent) took antibiotics.

The increased miscarriage risks associated with different antibiotics ranged from a 65 per cent increase for azithromycin to almost triple the risk for quinolones, which are already not recommended for use in pregnancy.

The researchers got similar results when they compared these antibiotics to penicillin, which they note is the most commonly used antibiotic in pregnancy, and has been most widely researched for use in pregnancy.

The results suggest that certain antibiotics may increase miscarriage risk. The study, which was led by Anick Berard, PhD, of the University of Montreal, was published online in CMAJ on May 1, 2017.

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  • A publication of:
  • Women's College Hospital