It's not a statistic that is talked about often, but more than 10 percent of the babies in the U.S. are born prematurely. What can be done?

We have known for a while that vaginal infections are somehow related to preterm births. A team of researchers from Washington University School of Medicine in St. Louis decided to drill down into the mix of microbes found in the vagina during pregnancy and come up with some answers. They learned that a decrease in the diversity of vaginal microbes of pregnant women between the first and second trimesters is a predictor of preterm birth.

“We now know there is a difference in the vaginal microbes of women who are going to deliver early, and this study also showed us that these changes happen far earlier in pregnancy — months before delivery — than we expected,” said Molly Stout, MD, an assistant professor of obstetrics and gynecology and the study’s lead author. “We wanted to study this problem in a predominantly African-American population because their rates of preterm birth are much higher than in other groups.”

The study followed 77 pregnant women. The researchers examined the vaginal microbiome by obtaining vaginal swabs at routine prenatal visits and sequencing the DNA of the microbes on the swabs. Twenty-four of the women delivered at least three weeks early.

Typically, women at risk of delivering their babies early are handled with a large suite of treatments. These may include antibiotics, hormones, bed rest and even a surgical procedure that closes the cervix during pregnancy. The research out of Washington U/St. Louis may inspire scientists to devise more targeted therapies that are focused solely on the microbiome. Possible approaches may include therapies to alter the microbiome, predicting early delivery to get patients in rural areas who are at risk of preterm birth to tertiary care centers before delivery, and giving pregnant women steroids before delivery to help their babies survive.

“Almost 400,000 babies are born prematurely in the United States each year, and these births have lifelong consequences,” Stout said. “The sooner we figure out what is going wrong in a pregnancy in which a woman delivers early, the sooner we will be able to design new treatments to help women carry their babies to full term.”

The research has been published in the American Journal of Obstetrics & Gynecology.