Could taking antibiotics during pregnancy or breastfeeding impact your child’s behaviour?

There’s nothing worse than developing an infection when you’re pregnant. As if the morning sickness and several pounds of pressure weighing on your bladder weren’t enough, you have to deal with new uncomfortable symptoms from, say, strep throat or a UTI. The other problem? Researchers are beginning to raise questions about how that penicillin your doctor prescribes to help you get better will affect your growing baby. In fact, the latest research on this front suggests that taking low-dose antibiotics during pregnancy or breastfeeding could have long-term effects on a child’s gut health and their behaviour.

The study, which was conducted by researchers from the McMaster Brain-Body Institute at St. Joseph’s Healthcare Hamilton and published in the journal Nature Communications, found that giving low-dose penicillin to pregnant and lactating mice changed the balance of gut microbes in babies. It also impacted behaviours in their young—increasing social problems and aggression, and decreasing anxiety in a way that led to the young mice putting themselves in vulnerable situations. Importantly, the research also found that when mothers were given a probiotic along with the antibiotic, some of these problems were prevented.

Of course, one of the biggest questions scientists need to answer is whether what happened in the mice is also happening to people, but it’s not an unreasonable leap. Previous research in humans has proven that antibiotics affect infant health in other ways, such as increasing their likelihood of developing allergies. And other studies in mice have suggested that early antibiotic exposure could lead to obesity.

In this study, pregnant mice were given a dose of penicillin—akin to the amount that would be prescribed to infants—from the last week of pregnancy until their babies were weaned. They were compared to a control group, as well as to a group that was given penicillin for half the day and the probiotic Lactobacillus rhamnosus for the other half. Those who just received antibiotics saw a lasting impact on the health of their gut microbes and were less social and more aggressive. Some of these changes were still observed in those who received a combination of antibiotics and probiotics, but the effects were diminished. The researchers also saw changes in the brains of mice who received antibiotics, including signs of inflammation.

Because prescribing antibiotics in the first few years of life is extremely common—they’re the most frequently dispensed drugs in children worldwide—it’s important that to know what impact they’re having on kids. And prescriptions aren’t the only way children are exposed to antibiotics; John Bienenstock, one of the study’s authors and the director of the Brain-Body Institute, points out that they’re also found in meat products, which could raise further questions.

“We’re waving a warning flag that we’re going to have to find out more information in this area clinically,” says Bienenstock, who is also a professor of pathology and molecular medicine at McMaster University in Hamilton, Ont. But that doesn’t mean you should refuse antibiotics when your doc prescribes them. “There are all sorts of infections that people get in which penicillin or even stronger antibiotics are really necessary and save lives,” says Bienenstock. “And we don’t want to stop that.”

Though it’s too soon to know exactly how to prevent potential effects antibiotics might have on children and when antibiotic exposure could be harmful—whether it’s during pregnancy or after birth—Bienenstock sees the early evidence for probiotics as promising. “We certainly show that antibiotics change things for the worse, and those effects are largely prevented by taking the probiotic.”

There are all kinds of questions surrounding species and doses of probiotics, and there are no accepted recommendations for giving probiotics to infants or kids, but when it comes to probiotic-containing foods, things like yogurt or kefir are safe options.

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