Ask the Experts

A: Most people know that a pregnant woman needs to take care of her intestinal and vaginal flora (microbiota) to ensure she’ll share the best mix of bacteria when her baby is born and passes through the vaginal area.

Even if the baby is born via Caesarean section, the mother’s balanced gut microbiota helps prevent possible infections. What most people don’t realize is that after the baby is born, the mother continues to have an impact on her baby’s microbiome.

A few studies have shown that we constantly exchange our microbes by being in contact with one another. This is probably why members of the same family that live in close proximity tend to experience the same health issues or share a protection, even if sometimes they are not even genetically related. (We exchange up to 80 million bacteria when we kiss.)

This is even more true for babies if the mother is breastfeeding—not only because she shares her antibodies in the milk, but also because she is sharing her gut microbiota. Scientists knew mothers were sharing some bacteria when breastfeeding, but it was thought the baby was getting mostly skin bacteria and a little from the breast milk.

Recent studies have shown it is more than that. In fact, a phenomenon occurs after giving birth that seems to allow bacteria to pass through the intestinal barrier; mother’s milk contains much more bacteria than we thought.

The exact mechanism and whether it migrates via the blood or the lymphatic system is not totally understood, but we know there is a good exchange of the flora through breastfeeding.

For these reasons, I always recommend a prenatal probiotic formula to pregnant women, and encourage them to continue using it at least until they stop breastfeeding.