A landmark study published in the American Journal of Obstetrics and Gynecology (AJOG) found women with a short cervix treated with vaginal progesterone showed a decreased rate of preterm birth by 42%, and significantly reduced the rate of respiratory distress syndrome and the need for mechanical ventilation, as well as a composite of several complications of premature newborns (e.g. infection, necrotizing enterocolitis, intracranial hemorrhage, etc.).

"Our analysis provides compelling evidence that vaginal progesterone prevents preterm birth and reduces neonatal morbidity/mortality in women with a short cervix," said lead investigator Dr. Roberto Romero, Chief of the Perinatology Research Branch and Head of the Program in Perinatal Research and Obstetrics of the Division of Intramural Research for the NICHD/NIH/DHHS, Bethesda, MD and Detroit, MI. "Importantly, progesterone reduced early preterm birth (those occurring before 33 or 28 weeks of gestation). These immature babies are at the greatest risk for complications, death, and long-term disability (e.g. cerebral palsy). Progesterone also decreased a fraction of 'late preterm births,' which are the most common preterm deliveries. The profile of adverse events was no different from placebo.