Montreal, Canada—Which antibiotics are more safe and less safe for pregnant women to use? A new Canadian study provides some straightforward answers.

The report, published in the British Journal of Clinical Pharmacology says that in utero exposure to clindamycin, doxycycline, quinolones, macrolides, and phenoxymethylpenicillin appears to be linked to organ-specific malformations.

On the other hand, amoxicillin, cephalosporins, and nitrofurantoin, were not linked with major congenital malformations (MCMs) reports the study team led by researchers from the University of Montreal.

For the study, researchers analyzed information on 139,938 live births in Quebec, Canada, between 1998 and 2008, following women 12 months before and during pregnancy. Antibiotics exposure was assessed in the first trimester and MCMs were identified within the first year of life.

Adjusted results indicate that clindamycin exposure was associated with an increased risk of MCMs (aOR 1.34, 95%CI, 1.02-1.77, 60 exposed cases), musculoskeletal system malformations (aOR 1.67, 95%CI, 1.12-2.48, 29 exposed cases) and ventricular/atrial septal defect (aOR 1.81, 95%CI, 1.04-3.16, 13 exposed cases).

Doxycycline exposure increased the risk of circulatory system malformation, cardiac malformations and ventricular/atrial septal defect (aOR 2.38, 95%CI ,1.21-4.67, 9 exposed cases; aOR 2.46, 95%CI, 1.21-4.99, 8 exposed cases; aOR 3.19, 95%CI, 1.57-6.48, 8 exposed cases, respectively).

Single defects were detected when the expectant mothers took quinolones, moxifloxacin, ofloxacin, macrolides, erythromycin, and phenoxymethylpenicillin. No such issues were observed with amoxicillin, cephalosporins, and nitrofurantoin.

The authors reported similar results when penicillins were used as the comparator group.

Although the absolute risks for birth defects were quite small, the researchers urged physicians to consider prescribing other antibiotics when treating patients with infections during pregnancy.

“Infections during pregnancy are frequent and should be treated; however, our study highlights safer options for the treatment of infections, more specifically urinary tract infections or pulmonary infections, at least during the first trimester of pregnancy,” explained senior author Anick Bérard, PhD, of the University of Montreal.

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