Researchers at Baylor College of Medicine and Texas Children’s Hospital found that the placenta is not free from bacteria or other living organisms, but rather harbors a unique microbiome, bringing new insights on how the organisms present in the placental structure can impact a pregnancy.
Lead author of the report, Dr. Kjersti Aagaard, professor of obstetrics and gynecology at BCM and the Texas Children’s Pavilion for Women, explained that the team noted that “the most abundant microbes in the mom’s vagina were not what populated the baby’s intestinal micro biome.” Having found this, they figured there should be another source feeding the fetus, and started to examine the placenta.
The human microbiome is the aggregate of microorganisms that cohabit in our bodies, helping cells complete their tasks. Despite recent demonstrations of an intracellular bacteria with diverse metabolic and immune regulatory functions, the placental microbiome has not been extensively analyzed. In the study, published in the current issue of the journal Science Translational Medicine, Aagaard and her colleagues focused for the first time on the placental microbiome.
The team analyzed 320 subjects with extensive clinical data, comparing placental specimens from these subjects, collected under sterile conditions. They identified a unique placental microbiome niche and noticed that, rather bearing similarities to anatomically close microbiomes, the placental microbiome profiles were most similar to the human oral microbiome.
Escherichia coli, a bacteria that lives in the intestines of most healthy individuals, was the species with the highest abundance in most individuals. Prevotella tannerae and non-pathogenic Neisseria species, both species of the oral cavity, were also detected in highest relative abundance.
In this light, researchers stress the importance of oral health during pregnancy, as theses findings reinforce data relating periodontal disease to risk of preterm birth.
Further analyses on some of the subjects revealed associations of the placental microbiome with remote histories of antenatal infection, such as urinary tract infection in the first trimester, as well as with preterm birth.
A larger study is currently underway to expand these findings to describe the placental and microbiome profiles across pregnancy and in relation with preterm birth. With further developments, researchers hope to get a clearer picture of how several microbiome in women and their plancetas change over the course of the pregnancy among those at risk for preterm birth.
“These discoveries could lead to rapid breakthroughs in not only identifying women at risk for preterm birth, but developing new and worthwhile strategies to prevent preterm birth,” said Aagaard.
Additional authors include Jun Ma, Dr. Kathleen M. Antony, Dr. Radhika Ganu and Dr. Joseph Petrosino, all from Baylor.
Funding for this work was provided by the National Institutes of Health Director’s New Innovator Award (to Aagaard); the Burroughs Welcome Fund Preterm Birth Initiative (to Aagaard and Versalovic); the National Institutes of Health’s National Human Genome Research Institute as well as the Director’s Common Fund (to Aagaard, Versalovic, and Petrosino); and the Alkek Center of Metagenomics and Microbiome Research (led by Petrosino with funding awards to Ganu and Aagaard).