From avoiding sushi to obsessive hand-washing, many pregnant women—with good reason—do everything in their power to avoid becoming sick. But when a woman does develop a minor ailment like a cold during pregnancy, she may be strongly tempted to seek out antibiotics—just to be on the safe side. But a new study adds to evidence that this might not be a good idea.

Researchers at the University of Chicago Medicine have found that antibiotics given to mother mice during the peripartum period (just before and after giving birth) resulted in gut microbiota dysbiosis and immune system changes, as well as a higher risk of inflammatory bowel disease, in their genetically-susceptible offspring.

The group of researchers carried out the study in mouse mothers and offspring that were both genetically prone to developing inflammatory bowel disease. They studied what happened to the offspring when the mothers received the antibiotic cefoperazone late in pregnancy and throughout the peripartum period.

Not only did the researchers see a decrease in overall diversity of bacteria in the maternal guts, they also saw a decrease in populations of the phylum (i.e. group) Bacteroidetes, with a relative increase in both Firmicutes and Verrucomicrobia. These changes didn’t go away even 4 to 8 weeks after the end of the antibiotic treatment.

The lasting changes in the gut microbiota of the mother mice didn’t seem to affect their own susceptibility to inflammatory bowel disease, but it did affect their mouse pups. The pups were born with gut microbiota dysbiosis and reductions in cells with anti-inflammatory effects, and had a greater chance of developing disease as they grew older. The authors hypothesized that because the antibiotic-related dysbiosis happened in early life, during a “critical developmental window for gut microbial assemblage and immune programming”, it had greater consequences for them than for their mothers.

Whether the findings apply directly to humans is still unclear. But questions persist about the effects of antibiotics during the peripartum period in humans, since several population studies (see here and here, for example) have shown that early-life exposure to antibiotics goes hand-in-hand with a higher risk of IBD development in childhood. A recent survey from Denmark found about 40% of pregnant women had at one or more courses of antibiotics during their pregnancy.

While this work underscores the importance of the maternal gut microbiota in pregnancy for the health of the offspring, the authors emphasize that if a pregnant woman is prescribed antibiotics by her doctor, she should definitely follow through with taking them.

“Antibiotics should absolutely be used judiciously when they’re indicated,” says Professor Eugene B. Chang, MD, senior author of the study. “But we as physicians should keep in mind the importance of antimicrobial stewardship.” The study, in other words, is a reminder that best practice, whether during pregnancy or not, is to avoid casual or “just in case” antibiotic usage.



Miyoshi J, Bobe AM, Miyoshi S, Huang Y, et al. Peripartum Antibiotics Promote Gut Dysbiosis, Loss of Immune Tolerance, and Inflammatory Bowel Disease in Genetically Prone Offspring. Cell Reports. 2017; 20(2): 491–504.