Preterm deliveries play a significant role in neonatal morbidity and mortality. Previous studies showed that administration of progesterone to pregnant women at high risk, decrease spontaneous preterm deliveries.

The purpose of this study is to compare between two different modes of treatment with progesterone for the prevention of preterm delivery: weekly injection of 17 alfa hydroxyprogesterone caproate versus daily vaginal administration of progesterone in terms of efficacy, comfort and compliance, safety and cost of treatments.

Inclusion Criteria:

• The subject has a history of spontaneous preterm delivery defined as earlier than 37 gestational week.
• The subject has a short cervical length defined as 25 mm before 24 weeks gestation.
• A singleton gestation.

Exclusion Criteria:

• Multifetal pregnancy.
• The subject has or will have a cervical cerclage in place.