Common antibiotics may double miscarriage risk: study

Women who take common antibiotics to treat infections during the early stages of pregnancy may be at two-fold increased risk of suffering a miscarriage, a new study warns.

Researchers from Universite de Montreal in Canada looked at data from about 8,702 cases, defined as clinically detected spontaneous abortions, which were matched with 87,020 controls. The mean gestational age at the time of miscarriage was 14 weeks of pregnancy.

A total of 1,428 (16.4 per cent) cases were exposed to antibiotics during early pregnancy compared to 11,018 (12.6 per cent) in controls. Participants were between the ages of 15 and 45 years.

Researchers found that many classes of common antibiotics, such as macrolides, quinolones, tetracyclines, sulfonamides and metronidazole, were associated with an increased risk of miscarriage in early pregnancy. They also found that women who miscarried were more likely to be older, living alone and to have multiple health issues and infections, all of which were taken into account in the analyses.

Erythromycin and nitrofurantoin often used to treat urinary tract infections in pregnant women were not associated with an increased risk, researchers said.

"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," said Anick Berard from Universite de Montreal.

"Given that the baseline risk of spontaneous abortion can go as high as 30 per cent, this is significant," Berard said.
The study was published in the Canadian Medical Association Journal.