First of its kind trial will analyze effectiveness of vaginal live biotherapeutic to lower preterm birth in high-risk women
ARLINGTON, VA, May 13, 2026 — March of Dimes, a national leader in maternal and infant health research, today announced the start of a historic preterm birth clinical trial at its Prematurity Research Center (PRC) at Imperial College London. Through this trial, scientists are testing whether a vaginal live biotherapeutic containing good bacteria can lower rates of preterm birth in high-risk women. The study is a result of March of Dimes’ nearly decade long, $10 million investment into live biotherapeutic research at the Imperial PRC to stop early labor.
The “gold standard” Randomized Controlled Trial (RCT), which has begun recruiting patients in London, is testing whether pregnant women who take a live biotherapeutic containing Lactobacillus crispatus bacteria, which is associated with a healthy reproductive system, experience fewer preterm births than women given a placebo. A previous feasibility study by March of Dimes PRC scientists at Imperial showed a 50% reduction in preterm birth rates in women taking the bacteria.
Called FLIP-2, a nod to ‘flipping the flora’ in the vaginal canal from bad to good, the trial is being funded primarily by March of Dimes, which has invested over $10M since 2018 into research on the safety and efficacy of using a live biotherapeutic to prevent preterm birth, as well as into the cost of running a multi-site RCT.
As a result, FLIP-2 is the first RCT testing the value of a live biotherapeutic to prevent preterm birth, carrying the potential to bring to market one of the first therapeutics in decades to combat early labor, a leading cause of infant mortality worldwide.
“This trial is one of the most promising and consequential studies preterm birth scientists have undertaken in a very long time,” said Dr. Emre Seli, Chief Scientific Advisor, March of Dimes. “Getting here has taken time, resources, and commitment to the promise of good bacteria as a key modulator of inflammation in the female reproductive tract. Our field hasn’t seen a new therapy to stop preterm birth in decades – it’s safe to say we’re all rooting for this one to buck the trend.”
If successful at reducing rates of preterm birth in Europe, the biotherapeutic would move to a third phase clinical trial in the U.S., and if results here are also positive, would begin the process of regulatory review ahead of commercial availability, transforming the landscape of pregnancy and birth. Microbiome-driven preterm birth, or preterm birth due to inflammatory bacteria inside a woman’s vaginal canal, is believed to account for up to 40% of all early birth.
“As a high-risk obstetrician whose heart breaks every time I have to tell a patient who delivered early that I don’t know why this happened or there’s nothing else that could have been done, this trial could not come sooner,” said Dr. Lynne Sykes, Parasol Foundation Associate Professor at Imperial College London and one of two principal investigators of the FLIP-2 trial at the Imperial PRC. “We’ve seen the benefits of this bacteria time and time again in our labs, so it’s hard to overestimate the hope we have for this study, the women in it, and all the women who will hopefully come after them.“
Preliminary findings from FLIP-2 are expected in 2029. They will include validation of a breakthrough March of Dimes-funded device made by Imperial PRC scientists to identify vaginal microbiome bacteria and corresponding inflammatory status in minutes.
About March of Dimes
March of Dimes leads the fight for the health of all moms and babies. We support research, education, and advocacy, and provide programs and services so that every family can have the best possible start. Since 1938, we’ve built a successful legacy to support every pregnant person and every family. Visit marchofdimes.org or nacersano.org for more information. Find us on Facebook and follow us with #marchofdimes and @marchofdimes.
Contact: Erin DeGiorgi
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