PROLONG Clinical Study Protocol: Hydroxyprogesterone Caproate to Reduce Recurrent Preterm Birth.

The objective of this commentary is to describe the background, rationale, and methods of the PROLONG (Progestin's Role in Optimizing Neonatal Gestation) trial, which is a multicenter, multinational, placebo-controlled, randomized clinical trial (RCT) designed to assess the safety and efficacy of Makena (hydroxyprogesterone caproate injection, 250 mg/mL) in reducing the risk of preterm birth (PTB) and neonatal morbidity/mortality in women pregnant with a singleton gestation who had a previous singleton spontaneous PTB. The total sample size of the RCT will include 1,707 women. The trial has two coprimary outcomes: PTB less than 35 weeks and a composite neonatal morbidity and mortality index. This study sample size will provide 90% power to assess for a 35% reduction in neonatal morbidity and mortality. Secondary outcomes will include 2-year follow-up of infants. The trial is ongoing and targeted to complete recruitment in 2018.