Common antibiotics may double miscarriage risk, warns study

The research should not make pregnant women fearful to take antibiotics they are carefully prescribed by their doctors, said Dr. Deborah Money, a professor of obstetrics and gynaecology at the University of British Columbia.

In a review of more than 95,000 women, ages 15 to 45 years old, from 1990 to 2009, at least 8,700 suffered a miscarriage during their first 20 weeks of pregnancy. The researchers accounted for this before finalizing their results.

Macrolides are commonly prescribed for respiratory infections, as well as some intestinal infections and skin infections, especially for those resistant to penicillin. "It is reassuring that our findings [agree] with other studies and with the current guidelines, which state that quinolone and tetracyclin should not be used during pregnancy", Bérard said.

Owing to the various infections that occur during early pregnancy, women tend to consume some antibiotics.

In general, an increased risk of spontaneous abortion was seen with the use of macrolides (except erythromycin), quinolones, tetracyclines, sulfonamides, and metronidazole during early pregnancy.

A total of 1428 (16.4 percent) cases were exposed to antibiotics during early pregnancy compared to 11 018 (12.6 percent) in controls.

"Given that the baseline risk of spontaneous abortion can go as high as 30 per cent, this is significant". For instance, Bérard and her team were the first to suggest nitrofurantoin, which is mostly used to treat UTIs, was actually linked to a decreased risk of miscarriage.

Without a clinical trial where some women are given antibiotics to treat an infection and others are not given antibiotics to treat that infection, the exact causal relationship can not be definitely known.

But the scientists also found Erythromycin and nitrofurantoin - often used to treat urinary tract infections in pregnant women - not associated with an increased risk. Yet, doctors have previously viewed nitrofurantoins as a safe UTI treatment during pregnancy.

It's important to note antibiotic use during pregnancy is not strictly forbidden. According to the CDC, between 1997 and 2003, 29.7 percent of women in the US reported using antibiotics three months before becoming pregnant or while pregnant, with penicillins being the most frequently reported. "Women should seek medical counsel to identify the best treatment option".

  • Joanne Flowers