Vaginal Progesterone for the Prolongation of Pregnancy After Arrested Pre-term Labor

Inclusion Criteria: 1. 18 years of age 2. Tocolytic treatment between 24+0 and 34+0 weeks 3. Patient's consent to participate in this study 4. 24 hours after tocolytic initiation and up to 3 days after finishing the tocolytic treatment 5. Arrest of preterm labor Exclusion Criteria 1. Contraindication to ongoing pregnancy including: 1. Suspected amnionitis during testing for eligibility- evidence of active infection including temperature ≥ 38.0°C and uterine tenderness, foul-smelling vaginal discharge, maternal tachycardia of 120 beats per minute or greater, or sustained fetal tachycardia of 160 beats per minute or greater 2. Evidence of significant placental abruption (contractions and significant bleeding from placental origin) 3. Intrauterine fetal death diagnosed at the time of admission 2. Major fetal malformation 3. Known maternal allergy to progesterone 4. Current use of progesterone at the time of admission 5. Epilepsy 6. Breast cancer 7. PPROM (preterm premature rupture of membranes) during testing for eligibility 8. Age below 18 years 9. Known active liver disease (elevated liver enzymes at twice the upper normal limit according to medical history or blood test that were taking doring standard medical care) 10. History of deep vein thrombosis 11. Major active psychiatric disorders (major affective disorders and psychotic disorders) 12. Uncontrolled chronic hypertension 13. Heart failure 14. Chronic renal failure 15. Pre-gestational diabetes with known target organ damage 16. History of spontaneous preterm delivery 17. Previous tocolytic treatment during the current pregnancy