Recently, a team of researchers led by Kjersti Aagaard from Baylor College of Medicine in Houston and Texas Children’s Hospital, under the principle of strict asepsis to avoid any possible bacterial contamination, collected specimens from the placentas of 320 mothers and performed genetic sequencing, and the results were astonishing to many: the placenta has a broad spectrum of bacterial ecosystems. The fetus in the womb is not as sheltered from the outside world as previously thought, but the placenta actually “harbors” a unique ecosystem of bacteria – and more surprisingly, these bacteria may originate from the mother’s mouth. Until recently, it was widely believed that the newborn’s gut was a sterile system at birth, and that intestinal flora entered the newborn from the mother’s vagina during birth and migrated to colonize the gut. Other microorganisms are gradually “collected” from outside during the first years of life. However, this theory was greatly challenged when bacteria were found in the meconium of newborns, the first stool in the first few hours of life. Recently, a team of researchers led by Kjersti Aagaard from Baylor College of Medicine in Houston and Texas Children’s Hospital, under the principle of strict asepsis to avoid any possible bacterial contamination, collected specimens from the placentas of 320 mothers and performed genetic sequencing, and the results were mind-boggling to many: the existence of a broad ecosystem of bacteria in the placenta. What is even more mind-boggling is that the bacterial flora of the placenta is most similar to that of the mother’s oral cavity, not the vagina or intestine. That is, the intestinal flora system is already established during fetal life, and these bacteria are “eaten” through the mother’s mouth. The researchers suggest that a possible mechanism is that bacteria from the mother’s mouth enter the bloodstream and reach the placenta, and may further enter the amniotic fluid via the fetal bloodstream, where they are ingested by the fetus and colonize the intestine. This finding completely overturns previous knowledge, but provides a plausible explanation for the earlier finding that periodontal disease in pregnant women increases the risk of preterm birth. Bacteria from periodontal infections in pregnant women can enter the bloodstream and reach the placenta and trigger preterm labor. A 2013 systematic review and meta-analysis completed by the Johns Hopkins School of Public Health showed that maternal infection during pregnancy increased the risk of early-onset neonatal infections, i.e., bacterial infections in newborns in the first 7 days of life. These two studies may also provide some evidence to support each other. An earlier independent study by the same research team using macaques has shown that feeding a high-fat diet to pregnant animals alters the gut microbiota of their offspring.