Vaginal Progesterone Treatment Halves Preterm Birth Rate

The risk of preterm birth and neonatal mortality and morbidity declined significantly in asymptomatic women with a short cervix treated with vaginal progesterone, according to a new study.

Researchers at the US National Institute of Child Health and Human Development (NICHD; Bethesda, MD, USA), the University of Pretoria (South Africa), the University of São Paulo (Brazil), and other institutions world-wide conducted an individual patient data meta-analysis of randomized controlled trials involving a total of five trials of high quality that included a total of 775 women and 827 infants. The researchers wished to determine whether the use of vaginal progesterone in asymptomatic women with a sonographically short cervix (less that 25 mm) in the mid-trimester reduces the risk of preterm birth and improves neonatal morbidity and mortality.

The results showed that treatment with vaginal progesterone was associated with a significant reduction in the rate of preterm birth, respiratory distress syndrome, composite neonatal morbidity, and mortality, birth weight lower than 1,500 grams, admission to the neonatal intensive care unit (NICU), and requirement for mechanical ventilation. There were no significant differences between the vaginal progesterone and placebo groups in the rate of adverse maternal events or congenital anomalies. The study was published early online on December 12, 2011, in the American Journal of Obstetrics & Gynecology.

“Our analysis provides compelling evidence that vaginal progesterone prevents preterm birth and reduces neonatal morbidity and mortality in women with a short cervix. Importantly, progesterone reduced early preterm birth,” said lead author Roberto Romero, MD, of the NICHD. “Immature babies are at the greatest risk for complications, death, and long-term disability. Progesterone also decreased the fraction of late preterm births, which are the most common preterm deliveries.”

Progesterone, a steroid hormone involved in the female menstrual cycle, pregnancy, and embryogenesis of humans and other species, has a key role in the maintenance of pregnancy, and a decline in progesterone or its activity has been implicated in the onset of parturition. A decline in progesterone during mid-trimester could lead to cervical shortening, which would predispose to preterm delivery, with the risk increasing as cervical length decreases.

Related Links:
US National Institute of Child Health and Human Development
University of Pretoria
University of São Paulo