The rebirth of progesterone in the prevention of preterm labor

To evaluate data since 2003 on the efficacy and safety of progesterone supplementation in the prevention of preterm labor.

A MEDLINE and Ovid database search (January 2003-September 2012) was performed using the search terms preterm, progesterone, and 17α-hydroxyprogesterone caproate. All relevant abstracts were reviewed.

For efficacy and safety data, the search was limited to randomized, double-blind, placebo-controlled trials with the primary outcome of preterm delivery, fetal loss, or neonatal morbidity or mortality. Quality of the studies was assessed using the CONSORT (Consolidated Standards of Reporting Trials) guidelines for reporting parallel-group randomized trials. Eleven articles were selected for review.

Preterm birth, prior to 37 weeks' gestation, remains the leading cause of neonatal morbidity and mortality in the US due to lack of treatment options. Recently, the use of progesterone to prevent preterm labor, deemed decades ago to be ineffective, has been reexamined. Progesterone formulations and dosage regimens varied greatly between studies. In patients with prior preterm birth or shortened cervix shown on transvaginal ultrasound, progesterone appears efficacious in reducing the rate of preterm birth. However, this benefit was not demonstrated in multiple-gestation pregnancies. Overall, progesterone was well tolerated and appeared safe for mother and fetus. More studies are needed to confirm the dosage regimen and population that will benefit most from progesterone.

Progesterone appears to be safe and efficacious in reducing the risk of preterm birth in a select group of high-risk women with prior spontaneous preterm births and those with an ultrasound-confirmed short cervix. Women with multiple gestations do not benefit from progesterone supplementation.