Early universal use of oral progesterone for prevention of preterm births in singleton pregnancy (SINPRO study): protocol of a multicenter, randomized, double-blind, placebo-controlled trial

Background Preterm birth accounts for 75% of perinatal deaths and more than 50% of long-term neurological disabilities. For a singleton pregnancy, progesterone treatment is effective in prevention of preterm birth in women with an asymptomatic short cervix or a history of preterm birth. However, a large proportion of preterm births still is not currently preventable. The aim of this study is to determine whether early universal use of oral progesterone before 14 + 0 weeks of gestation can prevent preterm birth better than universal screening of cervical length at 18 + 0 to 23 + 6 weeks of gestation, followed by progesterone treatment in those with a short cervix in singleton pregnancy. Methods This is a multicenter, randomized, double-blind, placebo-controlled trial registered with ClinicalTrials.gov on 12 February 2018. Eligible consecutive pregnant women with singleton gestation attending antenatal outpatient clinics will be recruited after receiving counseling and signing the written consent form. Transvaginal cervical length measurement will be performed at recruitment (before 14 + 0 weeks of gestation) and between 18 + 0 and 23 + 6 weeks of gestation. After randomization, women will be randomly assigned to either the treatment group (oral dydrogesterone 10 mg three times daily) or the placebo group, and medication will be started before 14 + 0 weeks of gestation. Assigned groups will be unblinded if the cervical length is <= 25 mm between 18 + 0 and 23 + 6 weeks of gestation, and the management option for short cervix will be discussed (oral progesterone, vaginal progesterone, or cervical cerclage). The primary outcome is preterm birth before 37 + 0 weeks of gestation. Discussion Progesterone is used extensively in part of the in vitro fertilization program as luteal phase support, and it is not associated with teratogenicity. Universal progesterone supplementation may be a better approach to prevent preterm birth. This large, multicenter, randomized, double-blind, placebo-controlled trial will provide the best evidence, leading to the best strategy for the prevention of preterm birth.