Progesterone for Prevention of Preterm Birth

Progesterone pessaries are now available on the Pharmaceutical Benefits Scheme (PBS) for the prevention of preterm birth from at least 16 weeks gestation. The PBS criteria require that the patient has a singleton pregnancy and either a short cervix or a history of spontaneous preterm birth.

Progesterone is critical for the maintenance of pregnancy. The recommended dosage to prevent preterm birth is 200mg daily, preferably at night. Therapy should begin during the second trimester and continue until the end of the 36^th week of gestation or until delivery.

A meta-analysis investigated the efficacy of vaginal progesterone in this setting. Vaginal progesterone was found to significantly reduce the risk of preterm birth at 33 weeks gestation or less (14% versus 22% for placebo). The number needed to treat (NNT) to avoid one preterm birth was calculated to be 12. Vaginal progesterone was also associated with a reduced risk of respiratory distress syndrome, low birth weight, and admission to neonatal intensive care. This study found no significant differences in the frequency of maternal adverse events or congenital anomalies in the vaginal progesterone group compared to the placebo group.