It is widely believed that the placenta is a completely sterile organ from which a fetus gains the oxygen and nutrients it needs. But new research from the Baylor College of Medicine in Houston, TX, may quash this theory; investigators found that the placenta harbors bacteria that could have implications for pregnancy.

For their study, recently published in the journal Science Translational Medicine, the research team analyzed placenta samples from 320 subjects.

The samples underwent a process called shotgun metagenomic sequencing, which allowed the team to closely assess the diversity of bacteria in the placenta, as well as identify specific microbes and their genetic pathway.

Explaining the reasons behind conducting this research, lead study author Dr. Kjersti Aagaard, associate professor of obstetrics and gynecology in the section of maternal fetal medicine at Baylor and the Texas Children’s Pavilion for women, says:

“After we completed our studies of the vaginal microbiome (the population of microbes – bacteria, viruses and fungi – that live in human cells) in pregnancy, we noted that the most abundant microbes in the mom’s vagina were not what populated the baby’s intestinal microbiome.”

“We reasoned that there must be another source ‘seeding’ the infant’s gut at birth, so we sought to examine the placenta,” she adds.