The Surprising Link Between Antibiotic Usage and Miscarriage Risk

Could the type of antibiotic you take increase your risk of miscarriage? A study raises some concerns and offers guidance.

Pregnancy is an exciting and anxious time. The end result is the miracle of having a baby, but your body experiences so many changes, you can’t help but worry about potential complications.

If you end up with an infectionsuch as a urinary tract infectionduring pregnancy, talk to your doctor about the type of antibiotic they want to prescribe. A 2017 study published in the Canadian Medical Association Journal found an increased risk of miscarriage with many common antibiotics.

Researchers from the University of Montreal analyzed data from more than 90,000 women from the Quebec Pregnancy Cohort between 1998 and 2009. The women in the study ranged in age from 15 to 45 and the data was collected on average at about 14 weeks into pregnancy. The researchers found that expectant mothers treated with macrolides, quinolones, tetracyclines, sulfonamides, and metronidazole had up to double the risk of suffering a miscarriage compared to women who didn’t take antibiotics or who took other types.

The type of antibiotic matters

Brian A. Levine, MD, an obstetrician and gynecologist and practice director of CCRM New York, says it is important to recognize that not all antibiotics were included on the list of potential medications that could cause harm. For example, two antibiotics often used to treat urinary tract infections in pregnant women, erythromycin and nitrofurantoin, were not associated with increased miscarriage risk. UTIs are one of the most common types of infections during pregnancy.

“Those that we use commonly in pregnancy every day were still deemed safe,” he says. “It is important to note that this was a retrospective chart review, and not the gold-standard study, a prospective randomized controlled trial (which would possibly be unethical if any of these antibiotics did in fact cause untoward outcomes). With that said, the spontaneous miscarriage rate can be as high as 33 percent, so anything that impacts the natural miscarriage rate is definitely worth investigating.”

Women should still seek treatment for UTIs

Women’s health expert Sherry Ross, MD, an obstetrician and gynecologist and author of the woman’s guide, She-Ology, also has reassuring words for those concerned about the study results. “The safer antibiotics in this study did not have an increase in miscarriages and would be the ones recommended for women trying to conceive or unsure of their pregnancy status,” she says.

Dr. Ross says she doesn’t want the findings to stop pregnant women from seeking treatment for UTIs. “Left untreated, UTIs can cause more damaging consequences than using acceptable antibiotics during pregnancy,” she explains. “Most importantly, make sure you discuss the pros and cons of UTI treatment options with your obstetrician and discuss ways to avoid recurrent infections during the rest of the pregnancy. If you are trying to conceive you would want to make sure you are taking the antibiotics not associated with an increase in miscarriage risk.”

In other words, expectant moms: Don’t panic. If you have any concerns, speak to your doctor—and check out these other essential questions to ask before taking antibiotics.