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The human gut is home to trillions of microorganisms that help to regulate digestion, the immune system and other crucial aspects of human health. During pregnancy, the composition and balance of microbes in the gut -- also called the gut microbiota -- play an important role in maintaining metabolism and immune health and contribute to a healthy gut ecology in a newborn baby, according to research published in May 2011 in the “American Journal of Clinical Nutrition.”

Maternal Health

A number of studies link a healthy gut microbiota during pregnancy to improved maternal health. According to a review published in the “Journal of Maternal-Fetal and Neonatal Medicine” in May 2013, probiotic supplementation during pregnancy significantly reduces the occurrence of gestational diabetes, lowers fasting glucose and decreases pre-eclampsia risk. Weight gain was also shown to be less among pregnant women who supplemented with probiotics compared to those who didn't. These results may occur because probiotics help the body to assimilate nutrients, convert food into energy and manage factors like insulin resistance. Probiotic supplementation during pregnancy may also prevent complications like preterm birth.

Infant Health

Scientific research also shows that probiotic supplementation during pregnancy improves health in infants -- at least for those who are born vaginally and breast-fed. The infant gut is basically sterile until it is colonized with bacteria found in the birth canal and the breast milk, according to the May 2011 “American Journal of Clinical Nutrition” article. Probiotics during pregnancy improve the mother's gut microbiota, which in turn supports a healthy immune system and gut ecology in the baby. A meta-analysis published in May 2012 in “Epidemiology” revealed that probiotic supplementation during pregnancy and after birth reduced the rate of atopic dermatitis -- also called eczema -- and other allergic phenomena. Breast-fed infants of mothers who supplemented with probiotics during pregnancy also have lower rates of diarrhea, colic and constipation between the ages of 2 and 6 months.

Supplements and Food Sources

Numerous probiotic supplements are on the market, with varying quantities and types of strains. Talk with your health care provider to find a high-quality probiotic supplement that is right for your body. Foods are also a source of probiotics. Cultured foods include sauerkraut, kimchee, kombucha, natto, miso, traditionally made dill pickles, kefir and yogurt. Including nonpasteurized cultured foods in your diet during pregnancy, along with probiotic supplementation, helps to maintain a healthy gut microbiota.

Quick Tips

Occasionally, beginning a probiotic protocol can lead to gas, bloating or skin eruptions, which is typically a sign that the healthy microbes are recolonizing the gut, so it's nothing to worry about. If side effects or symptoms last more than two weeks, consult your doctor. According to the University of Maryland Medical Center, probiotics may rarely cause an allergic reaction – call your doctor immediately if you experience itching, swelling or trouble breathing and discontinue use.