Most common antibiotics are associated with an increased risk of miscarriage in early pregnancy. Only two molecules are exempt from all suspicion.
Antibiotics are not automatic. Especially in pregnant women. When the force of the day dictates, doctors had better pay attention to the molecules they prescribe. Because certain classes are associated with an increased risk of miscarriage, quinolones for example. A study conducted by the University of Montreal (Canada) highlights a worrying link in the CMAJ.
Up to twice the risk
Before reaching these conclusions, researchers in Quebec analyzed the files of 8,700 women who had suffered a miscarriage. They were compared to those of 87,000 women whose pregnancies went well. Of these participants, nearly 12,500 received antibiotics while pregnant. This parameter strongly favors spontaneous abortions during the first months of gestation. On average, the incident occurred at 14 weeks gestation.
The most common antibiotics are affected by this finding. Azithromycin and metronidazole, for example, are linked to a 70% increased risk. The likelihood of pregnancy termination is even higher with other families of antibiotics. Quinolones and tetracyclines increase the danger to the fetus by 2.5.
Two classes cleared
Only erythromycin and nitrofurantoin pass the test successfully. A relief for researchers, because they are widely used to treat urinary tract infections in pregnant women. “Assuming that miscarriage can reach up to 30% of pregnancies, this result is significant”, estimates Dr. Anick Bérard, co-author of this study.
For its part, the Reference Center on Teratogenic Agents (CRAT) is rather reassuring. Most antibiotics are allowed during pregnancy. the CRAT has developed a scale to assist prescribers in setting prescriptions. Penicillins, beyond any suspicion, are widely preferred.
However, the task is complex for doctors following pregnant women. At the end of 2015, the same Quebec team concluded that macrolides do not increase the risk of fetal malformation. These same macrolides that promote miscarriages, with the notable exception of erythromycin.
>> Read our “Treatment” sheet: Antibiotics, reasoned use avoids the development of resistance
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