Good bacteria, healthy pregnancy

The human microbiome is a hot topic in medicine that has led to a whole new way of approaching health and disease. The microbiome refers to the trillions of bacteria and other organisms that live in our bodies. Thanks to new technology, we are able to identify specific types and quantities of bacteria colonizing distinct habitats in our bodies. As a result, there has been a big shift in thinking because we can prove that  bacteria play a vital role in good health. For women, the microbiome is particularly interesting because it changes in response to hormonal fluctuations throughout the menstrual cycle, throughout pregnancy and throughout life. It also changes in response to diet, body habitus, hygiene, antibiotic use and changes in the environment.

There has been a big focus on studying the microbiome in pregnancy and how it might relate to illness in the pregnant woman and her fetus. The microbiome has been shown to change during the course of pregnancy as a possible protective mechanism. The bacteria in the pregnant female intestine goes through very impressive adaptations so that in the third trimester she is actually able to process food more efficiently and get more calories from the same amount of food. So a woman’s body has a special way of making sure her baby gets all of the nutrition and energy it needs to grow in the last months of pregnancy.

A woman’s microbiome in pregnancy is also important because it helps establish her baby’s microbiome which is essential for developing a normal immune system. For example, we know that babies born from mother’s who are overweight before they become pregnant, as well as babies born from mother’s who gain too much weight during pregnancy do not have as many “good bacteria” in their gut.

A hugely important step toward establishing a normal newborn microbiome is exposure to the bacteria in the mother’s vagina during labor and delivery, as well as from her skin during breastfeeding. Perhaps due to altered exposure to the mother’s microbiome, babies born by cesarean section may be at higher risk for health concerns later in life including obesity, asthma, eczema and diabetes. Clearly, in some cases, cesarean birth is the only safe birth alternative. But for women contemplating elective cesarean section, this is another piece of evidence supporting the benefits of vaginal birth.

A surprising discovery is that the placenta actually has its own microbiome and is not a sterile environment as was previously assumed. In addition, the placental microbiome has an important role in establishing the fetal microbiome. Perhaps the most unexpected finding is that bacteria found in the placenta is actually most similar to the bacteria found in the mother’s mouth. This link might explain why gingivitis and oral infections could be related to negative health consequences for pregnancy including preterm labor and stillbirth. So, in addition to starting your prenatal vitamin in preparation for pregnancy, you should make sure you visit your dentist!

We are early in our research efforts into understanding how the changing microbiome might influence health and disease. It appears promising that restoration of a normal microbiome could promote health, and it is possible that a probiotic may be a good way to restore the “good” bacteria in your body. In the meantime, you can do your best to maintain a healthy microbiome and to help your newborn establish a good immune system by:

  • Avoiding excessive weight gain in pregnacy
  • Avoiding unnecessary antibiotics
  • Attempting vaginal birth when possible
  • Breastfeeding when possible
  • Seeing your dentist regularly


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