Conference Coverage
NEW ORLEANS – Could the cervicovaginal microbiome be responsible for some preterm births?
"It is a hot topic because there is increasing interest in medicine with regard to the microbiome and how our health is affected by it," said Dr. William Grobman, program chair for the Society for Maternal-Fetal Medicine’s annual meeting. "Preterm birth remains poorly understood, but there is intriguing evidence that its occurrence may be related to alterations in the microbiome."
To explore the potential relationship between cervicovaginal microbiota and preterm birth, Dr. Michal Elovitz, director of the maternal and child health research program at the University of Pennsylvania, Philadelphia, led a team in a nested case-control study of 46 women. She presented her results at the meeting.
Dr. Elovitz and her colleagues tested vaginal swabs taken from pregnant women during 20-24 weeks’ gestation, and again during 24-28 weeks. After the women delivered, the cervicovaginal specimens from women who had preterm deliveries were compared with those taken from women who delivered at term.
The researchers tested the DNA from the samples and characterized the microbial communities. Vaginal samples were characterized into community state types (CSTs) based on which bacteria dominated the microbial community. The first group, CST I, is dominated by Lactobacillus crispatus, which according to the Dr. Elovitz is traditionally considered a beneficial bacteria. CST III is dominated by L. iners, and CST IV is dominated by anaerobic bacteria, typical in bacterial vaginosis.
In the 14 women who had a preterm birth, the CST proportions were significantly different than those who delivered at term. In the preterm cohort, 17% had CST I, 61% had CST III, and 22% had CST IV.
In the term cohort, 35% had CST I, 37% had CST III, and 33% had CST IV (P = .012). The percentage of women who had no CST III was higher in women delivering at term than in those who delivered prematurely: 68% vs. 39% (P =.002).
"The percent of non–CST-III was significantly lower in samples from women delivering preterm than term. Notably, the differences in these microbial communities were evident in the late second trimester of pregnancy, weeks if not months prior to the preterm birth," said Dr. Elovitz.
Seventy-eight percent of the women in the study were black; Dr. Elovitz and her colleagues conducted a subanalysis of only those women. "And what we found is that the results were even stronger."
"The implications are very broad, and hopefully very clinically impactful. The microbiome is modifiable. We can find ways to change it," said Dr. Elovitz. The challenge now, she said, is to determine whether the microbiome is just a marker, or if it’s a cause. If microbiota are implicated, "there is a whole new window of opportunity for therapeutics to reduce preterm birth."
Dr. Elovitz did not have any relevant disclosures.