https://www.selleckchem.com/products/gsk1838705a.html Progestogens (vaginal progesterone and intramuscular 17-hydroxyprogesterone acetate) are widely recommended for women at high risk of preterm birth. Typical regimens include 17-hydroxyprogesterone caproate (250 mg intramuscularly weekly), starting at 16-20 gestational weeks until 36 weeks or delivery for women with a singleton gestation and a history of spontaneous preterm birth, or vaginal progesterone (90-mg vaginal gel or 200-mg micronized vaginal soft capsules) for women with a short cervix (typically ≤25 mm). Although some randomized trials support this approach, neither of the largest trials (PROLONG for 17-hydroxyprogesterone acetate or OPPTIMUM for vaginal progesterone) demonstrated efficacy. There are almost no data on long-term effects, and none that shows benefit beyond the neonatal period. Although some analyses suggest the cost-effectiveness of the approach, a cervical length screening program followed by progesterone for those with a short cervix will reduce preterm birth rates by less than 0.5%. The present review assesses evidence on the efficacy, likely impact, and long-term effects of implementing the recommendations for progestogens in full. Clinicians and pregnant women can look forward to resolution of the conflicting views on efficacy once the Patient-Centered Outcomes Research Initiative (PCORI)-funded individual patient data meta-analysis is published.Preterm birth is a live birth that occurs before 37 completed weeks of pregnancy. Approximately 15 million babies are born preterm annually worldwide, indicating a global preterm birth rate of about 11%. With 1 million children dying due to preterm birth before the age of 5 years, preterm birth is the leading cause of death among children, accounting for 18% of all deaths among children aged under 5 years and as much as 35% of all deaths among newborns (aged less then 28 days). There are significant variations in preterm birth rates and morta