Recurrent miscarriage is defined as three or more spontaneous miscarriages, with a prevalence of about 1%, and even after detailed medical examination, the cause of miscarriage is unknown in half of the couples. Recurrent miscarriage is associated with a poor prognosis and affects the pregnant woman and family members psychologically, therefore it needs to be actively evaluated and treated, but there is no effective treatment for this condition. Progesterone, which improves the endometrial status and facilitates embryo implantation, is important for the maintenance of pregnancy and is secreted by the corpus luteum early in pregnancy and provided by the placenta from 8 to 12 weeks of gestation. Therefore, it is of clinical importance to explore the efficacy of progesterone in recurrent miscarriage. A recent multicenter, double-blind, randomized, controlled clinical trial conducted by Coomarasamy et al. at the University of Birmingham Medical School in the United Kingdom suggested that progesterone preparations given early in pregnancy did not increase the risk of fetal malformations but did not improve neonatal live birth rates or perinatal outcomes in patients with recurrent miscarriage of unknown origin, and was recently published in N Engl J Med. Inclusion criteria: recurrent miscarriages of unknown origin in patients aged 18 to 39 years with a childbearing potential. Exclusion criteria: inability to conceive within the last 1 year, antiphospholipid syndrome, abnormal uterine morphology, chromosomal abnormalities in the couple, combination of underlying diseases such as diabetes or thyroid disease and systemic lupus erythematosus, anticoagulation therapy and other contraindications to progestogen use. After the first positive urine pregnancy (less than 6 weeks of gestation), the recurrent miscarriages were randomized into two groups: the test group was given 400 mg of vaginal progesterone gel twice/day, and the control group was given placebo until 12 weeks of gestation. The primary indicators were the live birth rate after 24 weeks of gestation, the secondary indicators were the gestational sac visible at 6-8 weeks of gestation, the fetal heartbeat visible at 12 weeks of gestation, the gestational week of miscarriage and delivery before 24 weeks of gestation, the survival rate at 28 days after delivery, and the congenital anomalies. Perinatal evaluation indicators: preeclampsia, premature rupture of membranes, infants younger than gestational age, prenatal hemorrhage, mode of delivery and birth weight of the newborn, umbilical artery blood PH, Apgar score, and the use of ventilator support. From June 23, 2010 to October 23, 2013, a total of 836 women conceived spontaneously, 404 in the progesterone group and 432 in the placebo group, with a follow-up rate of 98.8%. The live birth rate was 65.8% in the progesterone group and 63.3% in the control group. There was no significant difference in the incidence of adverse pregnancy events between the two groups, with a delivery rate of 3.8% in the progesterone group and 3.7% in the placebo group. The overall incidence of neonatal malformations was 3.5%, 3.0% in the progesterone group and 4.0% in the placebo group. There were no statistically significant differences in perinatal complications between the two groups. Previous studies have shown better efficacy of intramuscular progesterone, but controlled studies have shown that vaginal progesterone preparations are as effective as intramuscular in reducing the risk of preterm delivery and are easy to use. Therefore, in patients with recurrent miscarriage of unknown origin, progesterone preparations given early in pregnancy, although safe and without increased risk of fetal malformations, do not improve live birth rates or perinatal outcomes.