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What are the dangers of taking antibiotics at the beginning of pregnancy?
Last reviewed: 02.07.2025
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Canadian scientists examined almost 200 thousand pregnant women who, due to circumstances, had to be treated with antibiotics: macrolides, tetracyclines, fluoroquinolones, sulfonamides and metronidazole.
Today, medical professionals around the world suffer from a lack of information about the use of antibiotics at different stages of pregnancy: there is little data on the use of antibacterial agents, and clinical studies on this issue are rare. The fact is that most doctors avoid conducting any experiments on women during pregnancy - and this is absolutely logical. After all, no one can be sure that taking antibiotics will not affect the course of such an important physiological process.
Canadian scientists from the University of Montreal have confirmed that antibiotics can indeed pose a considerable danger, especially in the first trimester of pregnancy.
The experiment was based on data from the Quebec Pregnant Women's Organization (QPC), collected from 1998 to 2009. Thus, the study group consisted of almost 9 thousand women who had an early miscarriage. There were also women whose pregnancy went without incidents (almost 90 thousand). In total, the scientists analyzed almost two hundred thousand pregnancies.
At the end of the study, the scientists were able to discover that spontaneous miscarriages occurred mainly in those women who were forced to receive antibiotic treatment in the first trimester - in particular, macrolide, tetracycline group drugs, as well as fluoroquinolones, sulfonamide drugs and metronidazole. It is noteworthy that after treatment with azithromycin and metronidazole, the risk of miscarriage increased by approximately 70%, and after treatment with norfloxacin, spontaneous abortion occurred almost five times more often.
"These findings should lead healthcare practitioners to think about not prescribing antibiotics without first assessing the potential risks of taking them," said Professor Jason Newland, of the Infectious Diseases Society of America (IDSA).
However, as the study showed, not all antibacterial drugs are so dangerous for pregnant women. Fortunately, scientists did not find a connection between early miscarriage when treated with erythromycin and nitrofurantoin. The specialists also found confirmation that cephalosporin antibiotics and penicillin drugs are relatively safe.
"The findings of our experiments will be useful in clinical practice. It is very important that the recommendations for therapeutic prescriptions for infectious diseases in pregnant patients be reviewed," the researchers say. In addition, it is worth noting that the large number of participants in the experiment, as well as verified data on the antibiotic therapy administered and the facts of spontaneous termination of the gestation process, do not allow us to doubt the results of the study.