Antibiotics linked to risk of miscarriage in early pregnancy, study says

In some cases, the chances were increased by as much as 100 per cent

The link was seen with many classes of antibiotic (Getty Images/iStockphoto)

Common antibiotics could increase the risk of miscarriage in early pregnancy, new research shows.

According to a Canadian study, taking some drugs raises the chances of having a miscarriage by anywhere between 60 per cent and 100 per cent.

The worrying link was seen with a range of antibiotics including macrolides, quinolones, tetracyclines, sulphonamides and metronidazole.

That being said, nitrofurantoin – a drug used to treat urinary tract infections in pregnant women – had no effect on miscarriage risk; nor did erythromycin.

The study’s data was compiled from almost 9,000 cases of miscarriage at around 14 weeks and involved girls and women between the ages of 15 and 45.

“Infections are prevalent during pregnancy,” study leader Dr Anick Berard, from the University of Montreal in Quebec, 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% to two-fold increased risk.”

However, Dr Berard added that, “The increased risk was not seen for all antibiotics, which is reassuring for users, prescribers and policy-makers.”

The study also showed that women who miscarried were more likely to be older, to live alone and have additional health problems.

The findings, which are published in the Canadian Medical Association Journal, identified a total of 182,369 pregnancies from the Quebec Pregnancy Cohort - a large population group from the province providing data for ongoing studies. Of these, 8702 (4.7 per cent) ended with an early miscarriage.

“Use of macrolides (excluding erythromycin), quinolones, tetracyclines, sulphonamides and metronidazole during early pregnancy was associated with an increased risk of spontaneous abortion,” the research team concluded.

“However, residual confounding by severity of infection cannot be ruled out.”