The administration of vaginal progesterone, in addition to standard tocolysis, will decrease the risk of delivering prematurely and of recurrent preterm labor. We also hypothesize that the reduction in preterm delivery will be associated with a decrease in infant mortality and morbidity.

The principal aim is to demonstrate that progesterone reduces preterm birth before 37 weeks of gestation. Secondary aims are to show that progesterone 1) reduces preterm birth before 32 and before 34 weeks of gestation 2) reduces the number and duration of recurring episodes of preterm labor and 3) reduces infant mortality and morbidity.

Inclusion Criteria:

• Gestational age between 240/7 et 336/7 weeks of gestation (based on a reliable estimate by ultrasound performed before 22 weeks)

• Singleton pregnancy

• Intact membranes

• Preterm labor defined as:

  • 2 or more regular and painful uterine contractions in 10 minutes plus one or plus of the following criteria:
  • short cervix detected by vaginal ultrasound scanning (cervical length less than 30 mm until 31 weeks and less than 25 mm from 32 weeks)
  • cervical changes detected clinically (cervical length less or equal 10 mm or Bishop score less than 6
  • cervical changes during hospitalization (more or equal 5 mm between two clinical or US exams)
  • positive fetal fibronectin

• Age ≥ 18 years old

• Signed informed consent

• Possible and accepted follow-up

Exclusion Criteria:

• Multiple gestation
• Cervical cerclage
• Hydramnios (AFI >95th percentile for gestational age or greatest pocket >8 cm)
• Premature rupture of membranes
• Chorioamnionitis (criteria for clinical diagnosis are: elevated WBC, elevated CRP, maternal tachycardia, fetal tachycardia, uterine tenderness and/or amniotic fluid foul odor)
• Cervical dilatation > 3 cm
• Placenta praevia or abruptio placentae
• Intra-uterine growth restriction or non-reassuring fetal status
• Pre-eclampsia or severe hypertension
• Any other maternal or fetal pathology which should indicate medically preterm delivery