Antibiotics during pregnancy may increase miscarriage risk

Use of certain antibiotics early in pregnancy is associated with an increased risk for spontaneous abortion, the authors of a new study report.

Macrolides (except erythromycin), quinolones, tetracyclines, sulfonamides, and metronidazole all were associated with a greater risk, compared with penicillins, cephalosporins, or no antibiotic exposure at all, Flory T. Muanda, MD, and colleagues write in an article published in the May 1 issue of CMAJ.

The findings should be considered when guidelines are updated regarding treatment of infection during pregnancy, according to the authors.

This study was "well-conducted and highlights some of the potential negative consequences of using antibiotics in this population, especially if they're being prescribed inappropriately," Jason G. Newland, MD, MEd, associate professor of pediatrics, Washington University School of Medicine, St. Louis, and a spokesperson for the Infectious Diseases Society of America, told Medscape Medical News. He was not involved in the research.

To assess the potential effect of antibiotics on miscarriage risk, Dr Muanda, from the Faculty of Pharmacy, Université de Montréal, Quebec, Canada, and colleagues analyzed data from the Quebec Pregnancy Cohort on pregnancies that occurred between January 1998 and December 2009. The cohort is ongoing and includes information on all pregnancies among women covered by the Quebec Public Prescription Drug Insurance Plan.

Eligible patients were aged 15 to 45 years on the first day of gestation and continuously insured for at least 1 year before and during their pregnancy. Women who experienced a clinically detected spontaneous abortion before gestational week 20 were considered cases, with the calendar date of the spontaneous abortion designated the index date. For each case, the authors identified 10 control patients matched by age, year of pregnancy, and gestational date within 3 days.

Antibiotic exposure was defined as "having filled at least 1 prescription for any type of antibiotic either between the first day of gestation and the index date, or before pregnancy but with a duration that overlapped the first day of gestation," the authors explain.

The study included cephalosporins, macrolides, penicillins, quinolones, sulfonamides, tetracyclines, other antibacterial agents, antiprotozoals, and urinary anti-infectives.

Overall, 182,369 pregnancies met the inclusion criteria; of those, 8702 (4.7%) ended in spontaneous abortion, at a mean gestational age of 14.1 weeks (standard deviation [SD], 3.1 weeks; median, 14 weeks). The matched control group consisted of 87,020 pregnancies.

Antibiotic exposure occurred in 12,446 (13%) of those pregnancies, including 1428 that ended in spontaneous abortion (16.4% of all pregnancies ending in spontaneous abortion). Among the control patients, 11,018 (12.6% of all controls) were exposed to antibiotics (P < .001 compared with the cases).

Women who experienced a spontaneous abortion had a mean age of 28.7 years (SD, ¬±6.3 years) compared with women in the control group, who had a mean age of 27.8 years (SD, ±5.5 years' P < .001). They were also more likely to have been diagnosed with illnesses such as depression and asthma, to have visited a hospital or emergency department within the year before pregnancy, and to report more use of medications overall.

In an effort to account for these and other potential confounders, the authors analyzed a long list of covariates, including those associated with socioeconomic status, comorbidities, and demographics.

Follow NEWS.am Medicine on Facebook and Twitter