Researchers found that the risk of preterm birth appears to be linked to the types of bacteria in the vagina and cervix, with some species tied to a higher risk and others tied to a lower risk.
The study, led by the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, featured recently at the annual meeting of the Society for Maternal-Fetal Medicine in Las Vegas, NV, where it received the March of Dimes Award for Best Abstract on Prematurity. The abstract is published in the American Journal of Obstetrics & Gynecology.
Premature or preterm birth - defined as that which occurs before 37 weeks of pregnancy - is the leading cause of death worldwide among children under 5 years of age.
In 2015, around 1 in 10 babies born in the United States were premature.
Rates of premature birth in the U.S. fell between 2007 and 2014, partly due to reductions in the number of births to teenagers and young mothers.
More recently, however, preterm birth rates have begun to rise again, as Michal Elovitz, a professor in obstetrics and gynecology at Perelman and lead author of the study, explains:
"For the first time in 8 years, the number of preterm babies in the United States actually increased in 2016, and unfortunately, there are underlying causes that doctors still don't understand."
Babies born too early can experience serious problems, some of which can be lifelong. These include feeding difficulties, jaundice, problems with breathing, vision loss, developmental delay, vision loss, cerebral palsy, and hearing impairment.
In addition to these health problems, premature births incur an emotional and financial toll on families. At a national level, the burden can exceed $26 billion per year in "avoidable medical and societal costs."
Growing evidence of microbiota's role in health
There is growing evidence to suggest that changes in the microbe communities, or microbiota that live in and on our bodies, play an important role in health and disease.
Prof. Elovitz and colleagues note that while there have been some studies into a potential link between preterm birth and the microbiota of the cervix and vagina, they have been limited in both number and scope.
For their investigation, the researchers examined the microbiota in vaginal swabs of 1,500 pregnant women sampled at three different times during pregnancy: during weeks 16-20, weeks 20-24, and weeks 24-28.
Certain microbiota linked to premature birth risk
The team found that the risk of preterm birth varied in relation to certain species of microbiota.
In particular, higher levels of bifidobacterium and lactobacillus were linked to lower risk of premature birth, while higher levels of several anaerobic bacteria were linked to a higher risk.
The team validated the findings in a second analysis that looked at samples collected from 616 women during weeks 22-32 of their pregnancy.
Prof. Elovitz says that their study is distinctive because most others have limited their investigation to bacteria of the uterus.
She and her team call for further research to confirm their findings and begin to investigate whether targeting the "bad" bacteria or increasing the "good" bacteria might be an effective way to prevent premature birth.
"Decoding the causes of prematurity has been a riddle that's stumped researchers and clinicians for years, but our new study is finally shedding some light on a path toward offering treatment to women we can identify as being at-risk."
Prof. Michal Elovitz