According to a new study published Monday in the Canadian Medical Association Journal, many classes of common antibiotics were associated with increased risk of miscarriage when used in early pregnancy.
However, researchers did note that the increase in risk is small.
Dr. Anick Berard was the lead researcher and is a member of the Faculty of Pharmacy at the Universite de Montreal. She says that “it is reassuring to see that first-line treatments and antibiotics that are frequently used in the population (penicillin and cephalosporin) were not associated with increased miscarriage risk.”
Those antibiotics related to higher risk included macrolides, quinolones, tetracyclines, sulfanomides, and metronidazole. Doctors do not prescribe tetracyclines during pregnancy due to concerns over birth defects, and usually avoid quinolones as well.
Dr. Berard says that antibiotic prescribing patterns can differ from country to country, making it important to look at patient patterns. For this study her team looked at data from medical records of women in the Quebec Pregnancy Cohort between 1998 and 2009. The women ranged in age from 15-45 years old, covered by Quebec’s drug insurance plan. They compared pregnancy outcomes when various types of antibiotics were prescribed in early pregnancy.
From the data the team found 8702 cases of diagnosed spontaneous abortions, occurring on average at 14 weeks. They compared these cases with 87,020 pregnancies in which there was no miscarriage. Of the women who miscarried, 1428 (16.4%) had taken antibiotics early in their pregnancy. Antibiotic use was defined by filled prescriptions.
Generally, women who do not take antibiotics while pregnant have a miscarriage risk between 6% and 7%. The study showed that percentage increased to 10% with antibiotic use early term.
The women who miscarried were likely to be older and have multiple health issues and infections. Berard noted that the infections themselves could contribute to pregnancy loss and may play a role in increased risk. She says that “infections need to be treated during pregnancy” and advises women to discuss the best treatment option with their health care provider.
The American College of Obstetricians and Gynecologists does not provide a list of antibiotics that are safe to use during pregnancy but does offer physician guidelines. Dr. Phillip Heine is a member of that group’s Committee on Obstetric Practice and thinks it’s “unfortunate” that the new study did not allow for discussion on the limitations of the research. He says that many of the antibiotics associated with abortion are not used in obstetrics.
The safety of any particular antibiotic often depends on the patient’s individual diagnosis, making it critical to be informed and to fully discuss treatment with your doctor.