Microbiome is a complex community of microorganisms living on or inside human body. The locations of the microorganisms are skin, mouth, eyes, ears, gastrointestinal tract (the largest microbiome, mostly in the colon), respiratory tract, and urogenital tract. Microbiome is composed of approximately 40 trillion microbes, mainly bacteria but also fungi, protozoa, archaea, and viruses. The taxonomic ranking of microbiome includes Domain (highest level), Phylum, Class, Order, Family, Genus, and Species (lowest level). The diversity of microbiome is influenced by host genetics, mode of birth, age, gender, pregnancy, body mass index, diet, medication, and surgery. Microbiome is involved in the maintenance of human health. It impacts a variety of functions including regulation of immune system, protection against pathogens, digestion of food, production of vitamins, and regulation of body weight. Important changes affecting microbiome (dysbiosis) can be associated with or be the cause of several physiological and pathological conditions. Maternal microbiome plays an important role in shaping the immune system of the mother and the fetus, and the fetal neurodevelopment. Hormonal and dietary changes during pregnancy have important impact on microbiome. During normal pregnancy, oral microbiome undergoes stage-dependent changes by shifting towards a more pathogenic state. Gut microbiome is gradually enriched with bacteria that promote production and storage of energy, weight gain, and insulin resistance, all being essential for fetal growth and future breastfeeding. Vaginal microbiome decreases in richness and diversity, and Lactobacillus species becomes dominant. Dysbiosis during pregnancy can be associated with or cause several complications (e.g., preeclampsia, gestational diabetes, recurrent miscarriage, and preterm birth). Mode of birth has an important influence on the gut microbiome composition and the health of the newborn (immune development, metabolism, and disease risk). With vaginal delivery, infants are colonized by maternal vaginal bacteria (dominated by Lactobacillus genus), providing a better health protection for the infants. Following C-section delivery, infants are colonized by maternal skin bacteria (dominated by Staphylococcus, Corynebacterium, and Cutibacterium genera), exposing the infants to a higher disease risk. In conclusion, a healthy microbiome during pregnancy and delivery is essential for maintaining the overall maternal and newborn health and preventing pregnancy complications.

Hassan M Heshmati, Medical Doctor, Endocrinologist, has 50 years of experience in clinical research in Academia (University-Affiliated Hospitals, Paris, France and Mayo Foundation, Rochester, MN, USA), Pharmaceutical/Biotech Companies (Sanofi, Malvern, PA, USA, Essentialis, Carlsbad, CA, USA, and Gelesis, Boston, MA, USA), and personal Company (Endocrinology Metabolism Consulting, LLC, Hassan Heshmati and Valerie Shaw Endocrine Research, Anthem, AZ, USA). His research activity has been related to pituitary tumor, hyperthyroidism, thyroid cancer, osteoporosis, diabetes, and obesity. He has extensive knowledge in the development of anti-obesity products. He is the author of 358 abstracts, articles, book chapters, and book related to Endocrinology and Metabolism.