Drugs for the Treatment and Prevention of Preterm Labor.

Preterm birth refers to the delivery of a live fetus between 20 0/7 and 36 6/7 weeks' gestation. Tocolytics are used to inhibit myometrial contractions and subsequently, preterm labor/birth. The mainstay of tocolysis is to delay delivery for 48 hours to give adequate timing for the administration of antenatal corticosteroids that are proven to enhance fetal lung maturity and/or to transfer a patient to a tertiary care center. Vaginal progesterone is used to prevent spontaneous PTB (sPTB) in women with a shortened cervical length of 20 mm or less on transvaginal ultrasound without a history of a prior sPTB.