The complex picture of where the microbes are and why is becoming more complete - VERY INTERESTING!!!

Bacteria found in healthy placentas!! (Nature News)

The placenta, long thought to be sterile, is home to a bacterial community similar to the one found in the mouth, researchers report today. The microbes are generally non-pathogenic, but according to the authors of the study, variations in their composition could be at the root of common but poorly understood pregnancy disorders such as preterm birth, which occurs in one out of every ten pregnancies.

In 2012, Kjersti Aagaard, an obstetrician at Baylor College of Medicine in Houston, Texas, and her collaborators found that the most abundant microbes in an expectant mother’s vagina were different from those in a non-pregnant woman, but were not generally representative of those that were most common in the stool of an infant in its first week of life1. To investigate where these microbes were coming from, the team decided to examine the placenta.

In the new study, the researchers took samples of placental tissue from 320 women just after delivery, extracted DNA from the tissue and sequenced it. They found that the weight of the mother or whether she gave birth by caesarean or vaginally did not seem to change the makeup of the placental microbiome. But, Aagaard says, the bacterial community “was different among women who either experienced a preterm birth or had a much earlier infection, such as a urinary tract infection — even if that infection was treated and cured many months or weeks previously”. Their findings are published today in Science Translational Medicine2.

The amniotic sac in which a fetus grows is a sterile environment, but the placenta — an organ the fetus shares with the mother — is home to a bacterial community.