OBJECTIVE:To assess the efficacy of the Zishen Yutai Pill compared with placebo on live birth rates among women after fresh embryo transfer cycles.METHODS:We conducted a double-blind, multicenter, placebo-controlled, randomized trial to investigate whether administration of the Zishen Yutai Pill would improve pregnancy outcomes among women undergoing fresh embryo transfer after in vitro fertilization or intracytoplasmic sperm injection. The primary outcome was live birth rate. Secondary outcomes were rates of implantation, biochemical pregnancy, clinical pregnancy, pregnancy loss, cycle cancellation, and maternal, fetal, and neonatal complications. A total sample size of 2,265 women (1:1 in two groups) was used to detect a live birth rate difference between the Zishen Yutai Pill and placebo. Participants were enrolled and randomized to receive 5 g of the Zishen Yutai Pill or placebo orally, three times per day during the study.RESULTS:Recruitment was completed between April 2014 and June 2017, with 2,580 patients screened. Two thousand two hundred sixty-five patients were randomized: 1,131 to the Zishen Yutai Pill and 1,134 to placebo. Characteristics were similar between groups. In intention-to-treat analysis, the rates of live birth in the Zishen Yutai Pill (ZYP) group and placebo group were 26.8% and 23.0% (rate ratio [RR], 1.16; 95% CI 1.01–1.34; P=.038), respectively. The implantation rates were 36.8% and 32.6% in the ZYP and placebo groups, respectively (RR 1.13; 95% CI 1.01–1.25; P=.027). The biochemical pregnancy rate for the ZYP group was 35.5% compared with 31.1% in the placebo group (RR 1.14; 95% CI 1.02–1.28; P=.026). The rates of clinical pregnancy in the ZYP and placebo groups were 31.2% compared with 27.3%, respectively (RR 1.14; 95% CI 1.00–1.30; P=.043). There were no significant between-group differences in the rates of pregnancy loss, maternal, or neonatal complications (all P>.05).CONCLUSION:The Zishen Yutai Pill increased the rate of live birth after fresh embryo transfer compared with placebo.CLINICAL TRIAL REGISTRATION:Chictr.org.cn, Chictr-TRC-14004494.