The placenta is not as sterile as once considered. A new study has found that the placentas of healthy women contain several "good bacteria."

The study was conducted by researchers at the Baylor College of Medicine in Houston and colleagues. According to the team, the research shows that good germs play an important role in pregnancy.

"It allows us to think about the biology of pregnancy in different ways than we have before, that pregnancy and early life aren't supposed to be these totally sterile events," said lead researcher Dr. Kjersti Aagaard of Baylor College of Medicine in Houston, Associated Press reported.

Previous research has shown that the human body is home to billions of bacteria, some of which are good and aid digestion. Researchers had assumed that newborns gather good bacteria from their mothers during delivery.

The new study challenges this idea by saying that placentas of even healthy women contain germs. Scientists believe that the presence of certain "bad bacteria" might be linked to premature births. The research might also explain why women with certain infections tend to have premature births.

If confirmed, the study could be a relief to mothers who undergo caesarean sections. Previously, researchers had believed that babies born via C-section aren't exposed to good bacteria on their way to the world, which leads to poor development of the immune system. "I think women can be reassured that they have not doomed their infant's microbiome for the rest of its life," said Dr. Kjersti Aagaard, according to New York Times.

For the study, researchers obtained placentas from 320 pregnancies. The team then analyzed the genome of the bacteria present in the placenta. They found that bacterial community living in the placenta was "good" and mostly had strains of Escherichia coli, which are commonly found in guts. Other germs belonged to five main categories or phyla. Several bacteria belonged to organisms that help break vitamins in the body, according to Sciencemag.

The study is published in the journal Science Translational Medicine.