Taking some common types of antibiotics in early pregnancy can double the risk of miscarriage, according to a new study in Canada.
The research, published in the Canadian Medical Association Journal, found taking some classes of antibiotic raised the chances of miscarriage by between 60% and 100%.
“Our investigation shows that certain types of antibiotics are increasing the risk of spontaneous abortion, with a 60% to two-fold increased risk”
The link with was found with several types of the drug including most macrolides, quinolones, tetracyclines, sulphonamides and metronidazole.
However, nitrofurantoin – often used to treat urinary tract infections in pregnant woman – had no effect on miscarriage risk. The same was true of the widely used antibiotic erythromycin.
The research team from the University of Montreal and Centre Hospitalier Universitaire in Montreal looked at data on more than 95,000 pregnancies among women aged 15 to 45 from the Quebec Pregnancy Cohort.
These included more than 8,700 instances of miscarriage, which were matched with more than 87,000 control cases.
“Infections are prevalent during pregnancy,” said lead author Anick Bérard from the University of Montreal’s faculty of pharmacy.
“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,” she said.
“The increased risk was not seen for all antibiotics, which is reassuring for users, prescribers and policymakers”
The researchers took into account factors that can contribute to an increased risk of miscarriage including women’s age and general health.
However, they said they said could not rule out the fact “severity of infection” may have had an impact on the results of their analysis.
The research team hoped their findings would prove useful to policymakers when it came to issuing guidelines on the treatment of infections during pregnancy.
“The increased risk was not seen for all antibiotics, which is reassuring for users, prescribers and policymakers,” added Ms Bérard.