A new study is suggesting that some classes of common antibiotics if taken during early pregnancy can double the risk of miscarriage.
In the study, which was published on Monday in the Canadian Medical Association Journal, Macrolides, quinolones, tetracyclines, sulfonamides and metronidazole were related to higher rates of pregnancy loss, after a major review involving more than 95,000 women.
It is understood that the five common classes of the drug (mentioned above) were associated with an increased risk, while two others were shown to be safe.
The researchers said a greater chance of pregnancy loss was not seen with the most frequently used antibiotics, including penicillin and cephalosporin.
“It is reassuring to see that first-line treatments and antibiotics that are the most used in the population (penicillin, cephalosporin) were not associated with an increased risk of miscarriage,” Dr. Anick Bérard, lead researcher and a member of the Faculty of Pharmacy at the Université de Montréal, wrote in an email.
“Infections are prevalent during pregnancy,” the doctor said, adding that “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 60 per cent to two-fold increase.”
But the scientists also found Erythromycin and nitrofurantoin – often used to treat urinary tract infections in pregnant women – not associated with an increased risk.
In reaction, the Miscarriage Association said the scale and quality of the study made it “a really important piece of research.”
Dr Nicola Davies, a GP and former trustee of the association, said:
“The main risk this research throws up is for those women who don’t know they are pregnant.
“Most of these drugs are drugs you wouldn’t prescribe if you knew a woman was pregnant.”