New study: Antibiotic use during pregnancy may affect baby's gut health

When you're pregnant and you get sick, your OB/GYN has to look carefully at the risks and benefits of prescribing antibiotics. New research from the Winnipeg lab of Jean-Eric Ghia could affect the ways OBs measure these risks and benefits.

His research, conducted on mice, suggests that antibiotics during pregnancy increase newborns’ susceptibility to inflammatory bowel disease (IBD) by reducing their gut microbial diversity at a critical stage of development.

Ghia, an assistant professor and director of gastrointestinal basic biology research at the University of Manitoba’s IBD Clinical & Research Centre, explains his research in this Q&A.

Q: What does your new research show?

It shows that antibiotics given to mice during pregnancy affect the microbial composition of their newborns' intestines and reduce the microbial diversity. As a result of that, the baby mouse has a greater susceptibility to gastrointestinal diseases later in life. The findings show that reducing intestinal microbial diversity has implications for the maturation of the immune system and risk of a number of conditions such as asthma, diabetes and autism, but also of ulcerative colitis.

Q: What is novel here?

Research shows that antibiotic use in the immediate period after birth can severely alter gut microbiota in infants, and evidence from long-term studies suggests that these effects could last for months, if not years. Our new research shows that indirect exposure is also relevant, because gut microbial diversity was reduced in baby mice born to mothers who received antibiotics during pregnancy.

Q: How does giving antibiotics to a mother transmit to the baby?

Giving antibiotics to a mother before she delivers is going to modify the bacterial composition of her skin and also the microbiota in the vaginal wall, the uterine wall and the fecal microbiota around the birth area. This will affect what the baby is exposed to during birth.

Birth itself is a critical time for the baby to acquire bacteria, which then influences the initial immune system development. The baby is not going to see the same microbiota that he would normally have seen when he is born.

Q: Why is this study important for people if it was done on animals?

Doctors at our hospital have found many illnesses (such as asthma, allergies and other immune system disorders) in children related to early use of antibiotics. The reason we at the hospital’s research institute did this study, and the only reason we were able to, is precisely because it was done in animals. Such a study could never be done on actual babies. The way we did the study on the mice was that we checked the microbiota at two different levels: within the feces but also within the mucosa, because the microbiota in the feces is different from the microbiota in the gut wall. But in order to do that we had to take biopsies. To reproduce such a study in humans would involve a large-scale study that would have to be approved by an ethics committee. The other limiting factor would be the biopsies. I doubt that anyone—let alone the mother—would agree to their babies having three or four biopsies in its first few years of life!

Q: Would you say that your finding has implications for pregnant women?

Possibly. We were actually able to see the dysbiosis, or microbial imbalance, in the newborn mice and then to show that the newborns with dysbiosis were more susceptible to gut inflammation—we were the first to physically see this. This is similar to IBD, a disease that currently affects 250,000 Canadians and whose incidence is increasing every year. It is well known that dysbiosis is present in some IBD patients. So this is new knowledge that could have an impact on the IBD population of Canada.

Q: So what are you recommending, based on your findings?

Of course, antibiotics should be used in cases where there are concerns for group B strep or to reduce the incidence of postpartum maternal infection after cesarean section. GBS is the leading cause of life-threatening neonatal bacterial infections in developed countries; that is why we give antibiotics at the start of labour if there's a GBS concern.

Although prepartum antibiotics are also generally recommended for premature rupture of membranes, they are also frequently used in other clinical situations where there is no clear benefit.

Now the recommendation is that if it is a case of a mother being within a few days of delivery and a doctor is considering giving an antibiotic just for prevention, with no evidence of illness, or in a healthy woman, then perhaps the antibiotic should not be given. The antibiotic should only be given if there's a chance the mother or baby could develop an infection.

So for all the superfluous things, I would say that our study suggests not to take antibiotics because it could affect the first colonization and from that the maturation of the immune system.

Now, our findings are based on an animal model—so does it reflect what happens in humans? In the end, your OB/GYN needs to balance the risk-benefit ratio. I think that is the key message.

This article first appeared in and is condensed from The Medical Post on CanadianHealthcareNetwork.ca.

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