Factors that Affect the Microbiome During Pregnancy

Written by
Fathalla Ali, Bsc MSc, MPH and PHD student UNSW

Pregnancy is a complex physiological process associated with simultaneous hormonal, immunologic, and metabolic changes, which must all be synchronized to preserve the health of both the mother and the baby. Hormonal change is one of the first changes that occurs during pregnancy. It is characterized by a dramatic raise in the level of progesterone and oestrogen, which are important in fetus growth and development (1). The immunological changes or modulations are very complex, as on one hand, the immune system is supressed to help baby’s immune system development, whereas on the other hand, it protects the mother and baby from the infection. The metabolic changes during pregnancy resulted in changes in energy homeostasis, fat storage, and hormonal regulation (1). These changes are the same as those associated with metabolic disorder such as weight gain, increased fasting blood sugar level, insulin resistance and glucose intolerance (2). It is believed that, there are noticeable alterations in the composition of microbiota at different body sites coinciding with the hormonal, metabolic, and immune changes during pregnancy. These body sites include, gut, vagina, mouth and placenta as shown in the below figure (2).

Keywords: Microbiome, microbiota, pregnancy, hormonal changes, immunological changes, metabolic changes

Site at which Microbiota changes during pregnancy. “Adopted from Microbial changes during Pregnancy, Birth, and Infancy” (Nuriel-Ohayon, Neuman & Koren 2016, P.3)


  1. Neuman, H., & Koren, O. (2017). The Pregnancy Microbiome. Nestle Nutrition Institute workshop series, 88, 1–9. https://doi.org/10.1159/000455207
  2. Nuriel-Ohayon, M., Neuman, H., & Koren, O. (2016). Microbial Changes during Pregnancy, Birth, and Infancy. Frontiers in microbiology, 7, 1031. Click here.