SOURCES: Daniel DiGiulio, M.D., research associate and clinical instructor, medicine, Stanford University School of Medicine, Palo Alto, Calif.; David Relman, M.D., professor, departments of medicine and microbiology & immunology, and senior fellow, Freeman Spogli Institute for International Studies, Stanford University, and chief, infectious diseases, Veterans Affairs Palo Alto Health Care System; Molly Stout, M.D., MSCI, assistant professor, Maternal Fetal Medicine, Washington University in St. Louis; Josef Neu, M.D., professor, neonatology, University of Florida College of Medicine, Gainesville; Aug. 17, 2015, Proceedings of the National Academy of Sciences
MONDAY, Aug. 17, 2015 (HealthDay News) -- Researchers have come to learn how millions of germs carried in the body affect your health. Now, a new study links premature birth to a specific kind of bacterial blend in the vagina.
"Our discovery is important because it might allow us to determine which women are at elevated risk of premature birth by measuring the kinds of bacteria in their vagina early in pregnancy when there is still time to intervene and try to reduce the risk," said study co-author Dr. David Relman, a professor of medicine at Stanford University in California.
But this isn't going to happen soon. It's too early to know whether germs and premature births are actually connected. And if they are, researchers aren't sure what links them.
"Premature delivery is a hugely important problem in the U.S. and elsewhere around the world because of the increased likelihood of death or disability," Relman said.
About 450,000 infants are born prematurely -- more than three weeks early -- each year in the United States, the researchers said in background notes.
It's now known that the human body is filled with helpful germs. These microbes outnumber cells at least 10-fold and provide a variety of benefits, including protection from germs that can make people sick, said study lead author Dr. Daniel DiGiulio, a research associate and clinical instructor in medicine at Stanford.
In the new study, researchers examined germs from the guts, mouths and vaginas of 49 women. Samples were taken weekly during pregnancy and monthly for up to a year after birth. Fifteen of the women delivered prematurely.
Those who gave birth prematurely were more likely to have had greater bacterial diversity in the vagina, the study found. Women were especially likely to give birth prematurely if they had this pattern of bacteria for several weeks.
In some cases, the diverse germ community existed relatively early during pregnancy, DiGiulio said. "This is important because for over half of pregnant women who develop spontaneous preterm birth, we're never able to predict that their baby will be born prematurely or to determine in retrospect why that happened," he said.
One theory is that the germs set off the body's immune system, which releases proteins related to swelling and prompts labor, DiGiulio said. "Many of these proteins, such as a group of related molecules called 'cytokines,' are also thought to play a role in the initiation of healthy labor at term," he said.
Dr. Josef Neu, a professor of neonatology at the University of Florida College of Medicine in Gainesville, cautioned that the study findings are limited. While they're interesting, he said, the findings don't prove that certain bacterial patterns are related to premature birth.
"The data is preliminary, the number of subjects studied is small, and the lack of a clear mechanism of how altered vaginal microbes may cause preterm birth will require considerable additional research," Neu said.
Vaginal bacteria testing may one day become routine, but there's not enough evidence to support it now, he said.
Eventually, an antibiotic treatment might come along to adjust the makeup of bacteria in the vagina, he said. "It is entirely possible and even likely that some form of microbial therapy will be developed in the future that will lower the risk of premature birth," Neu said.
Dr. Molly Stout, an assistant professor of maternal-fetal medicine at Washington University in St. Louis, agreed that the study findings have potential to change practice. "All of this understanding and knowledge will hopefully lead us down a path to design better tests and treatments for preterm birth," she said.
The study is published in the Aug. 17 issue of Proceedings of the National Academy of Sciences.
For more about premature birth, see the March of Dimes.