Gut bacteria and pregnancy

Researchers from Bar-Ilan University have found that with pregnancy there is a change in the composition of gut bacteria in women. This could be associated with the changing hormonal status they speculate. The results of their study titled, “Progesterone Increases Bifidobacterium Relative Abundance during Late Pregnancy,” were published in the latest issue of the journal Cell Reports.

The authors write that pregnancy is associated with changes in the microbial profiles of the oral cavity, skin, vaginal cavity and the gut. There is a rise in “Proteobacteria, Actinobacteria, and opportunistic pathogens and a decrease in short chain fatty acid producers,” write the researchers.

A special form of bacteria called Bifidobacterium especially undergoes a growth in its population in the maternal gut say the researchers. This is usually prompted by the rise in progesterone levels in the mother’s blood. Bifidobacterium is known to be beneficial to new born babies. The researchers explain that it is as if the gut bacteria can sense the fact that the woman is pregnant.

Bacteria Bifidobacterium, gram-positive anaerobic rod-shaped bacteria which are part of normal flora of human intestine . 3D illustration - Credit: Kateryna Kon / Shutterstock
Bacteria Bifidobacterium, gram-positive anaerobic rod-shaped bacteria which are part of normal flora of human intestine . 3D illustration - Credit: Kateryna Kon / Shutterstock

The study researchers examine the effects of the microbiome due to pregnancy. Researchers Dr. Omry Koren of Bar-Ilan University’s Azrieli Faculty of Medicine and Prof. Yoram Louzon of the university’s Department of Mathematics. The researchers included those from Rabin Medical Center-Beilinson Campus in Petah Tikva. They noted that progesterone hormone can regulate the microbiome. This regulation can help the babies to develop they hypothesized.

Their study showed that during the late phase of the pregnancy there is a change in the composition of the bacteria especially Bifidobacterium. These bacteria can help break down the healthy sugars in the breast milk for the babies and help them grow. If the mother has high numbers of these bacteria in their gut, they can benefit their new born babies finds the study. In their study they noted an inflammatory response associated with rise in progesterone and in the mice Bifidobacterium was the significant bacteria that proliferated. When they administered progesterone to the mice from outside in controlled environments, they noted that the bacterial growth was similar to that seen during pregnancy.

The authors write in conclusion, “We found that the generally dominant bacteria during pregnancy were Blautia, Bifidobacterium (important for human milk oligosaccharide (HMO) degradation, unclassified Ruminococcaceae, Bacteroides, unclassified Lachnospiraceae, unclassified Clostridiales, Akkermansia, Faecalibacterium, Ruminococcus, and Prevotella (known to metabolize estradiol and progesterone). The genera that increased most significantly in the 3rd versus 1st trimester were Bifidobacterium, Neisseria, Blautia, and Collinsella. On the other hand, the genera Dehalobacterium and Clostridium as well as the Bacteroidales order were significantly higher in the 1st trimester versus the 3rd.”

Dr. Koren said in a statement, “Our results delineate a model in which progesterone promotes growth of Bifidobacterium during late pregnancy. The findings provide new insights into understanding the relationship not only between hormones and intestinal bacteria during pregnancy, but also for other conditions in which hormones are involved, such as progesterone supplementation as a component of fertility treatments or therapy in menopausal women.”

As a next step the team is looking to find the cause behind this change in the female gut microbiome during pregnancy.

Gut microbiome of pregnant mothers

A 2018 study titled, “The Maternal Gut Microbiome during Pregnancy,” published in the American Journal of Maternal/Child Nursing looked at the gut microbiome of pregnant mothers. Sara M. Edwards, lead author of the study from Laney Graduate School and Nell Hodgson Woodruff School of Nursing, Emory University and her colleagues write “Estrogen and progesterone also impact gut function, especially during the prenatal period. These physiologic changes in pregnancy allow for adjustments in maternal metabolism and weight necessary to support the pregnancy.”

The team concluded that much was left to be explored and when understood could help in development of therapies for a healthy pregnancy microbiome and healthy pregnancy outcome. They write, “The degree to which the gut microbiome contributes to the neurodevelopmental, immunological and intestinal health of the pregnant woman and her fetus is only now beginning to be measured. Health practices and novel therapies to promote eubiosis and treat dysbiosis of the maternal gut are still to be discovered but will likely prove fundamental in the care of women in pregnancy.”

Changes in gut microbiome in pregnant women with gestational diabetes

Another recent study by lead researcher Ilario Ferrocino from the Department of Agricultural, Forest and Food Sciences, University of Turin, Turin, Italy, looked at the changes in gut microbiota of pregnant women with gestational diabetes. The study was titled “Changes in the gut microbiota composition during pregnancy in patients with gestational diabetes mellitus (GDM)” and was published in the journal Scientific Reports.

The authors looked at 41 mothers with gestational diabetes and looked at their gut microbiome and its association with their diet. The fecal count of bacteria was noted for the women.

At the end of the study they noted a rise in “Firmicutes and reduction of Bacteroidetes and Actinobacteria” after following a healthy diet recommendation. The found that the rise in Faecalibacterium was associated with rise in fasting glucose in the mother. Collinsella and Blautia were also associated with insulin levels. Sutterella on the other hand was associated with C-reactive protein levels.

Authors concluded that “these findings suggest that the development of strategies to modulate the gut microbiota might be a potentially useful tool to impact on maternal metabolic health.”

To use or not to use probiotics in pregnant mothers

Proobiotics play a role in restoring normal gut microbiome. A study by Maria Elisabetta Baldassarre and colleagues from Neonatology and Neonatal Intensive Care Unit, Department of Biomedical Science and Human Oncology, “Aldo Moro” University of Bari, Bari, Italy, looked at the usefulness of use of probiotics in pregnant women.

The study titled, “Rationale of Probiotic Supplementation during Pregnancy and Neonatal Period,” was published in the journal Nutrients. The authors write about the useful effects of a healthy gut microbiome on immunity and development of the new born baby. They write, “a normal intestinal microbiota takes part in the induction of the immune tolerance.. (and) Alterations of the microbiota are associated with the development of many pathological states like infantile colic, inflammatory bowel disease, necrotizing enterocolitis, asthma, atopic diseases, celiac disease, diabetes, mood disorders, and autism spectrum disorders.”

The team says that guidelines suggest use of probiotics in pregnant women. They write, “In 2015, the WAO guidelines on the prevention of allergies recommends using probiotics in: (a) pregnant women at high risk for having an allergic child; (b) women who breastfeed infants at high risk of developing allergies; and (c) infants at high risk of developing allergies.”

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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