Abstract: Preterm birth is defined as birth between 28 and 37 completed weeks of gestation in China，and classified as either indicated preterm birth or spontaneous preterm birth. Preterm birth causes the major determinant of perinatal mortality and morbidity，and the long-term results of preterm birth often lead to neural and mental developmental defects. There is experimental support from animal and in vitro studies，and also empirical evidence from large randomized placebo-controlled clinical trials，that treatment with progestins（includes natural progesterone and its analogues） may reduce the risk of preterm birth. Progesterone has a role in maintaining pregnancy，by maintaining uterine quiescence and inhibiting cervical riping. This article reviews the use of progestins in women with high-risk factors for the prevention of spontaneous preterm birth and the safety of progestins supplementation in pregnancy.

Key words: Premature birth, Fetal membranes, premature rupture, Obstetric labor, premature, Progestins