IntroductionTo investigate whether rescue in vitro maturation (R-IVM) improves the reproductive outcomes among women undergoing intracytoplasmic sperm injection (ICSI) after one oocyte retrieved cycle. MethodsBetween January 2019 and December 2020, 2602 women who underwent ICSI in the Reproductive Medicine Center of Tongji Hospital, Wuhan, China, were included in our retrospective cohort study. There were 2112 women undergoing only ICSI and 490 women with R-IVM followed by ICSI. The intermediate reproductive outcomes and pregnancy outcomes were assessed, including the number of normally fertilized embryos, number of cleaved embryos, number of good-quality embryos, number of day-3 available embryos, number of embryos cultured past day-3, number of blastocysts, number of available blastocysts, biochemical pregnancy, miscarriage, clinical pregnancy and live birth. The perinatal outcomes were also assessed, including preterm birth and birth weight. The abovementioned outcomes were also calculated for in vivo matured and R-IVM oocytes separately in women undergoing ICSI with R-IVM group. Result(s)Compared with the women who underwent only ICSI, those who underwent ICSI with R-IVM had higher numbers of MII oocytes, normally fertilized embryos, cleaved embryos, day-3 available embryos, embryos cultured past day-3, and higher oocyte maturation rate, available embryo rate than women undergoing only ICSI. Additionally, we found that women undergoing ICSI with R-IVM had an increased chance of clinical pregnancy (adjusted OR=1.50, 95% CI: 1.17-1.93) and cumulative live birth (adjusted OR=1.35, 95% CI: 1.07-1.71). After propensity score matching (PSM), the cumulative live birth rate was 60.1% for women undergoing ICSI with R-IVM versus 54.9% for women undergoing only ICSI (OR=1.24, 95% CI: 0.94-1.63). The reproductive outcomes were also significantly different when calculated for in vivo matured and R-IVM oocytes separately in women undergoing ICSI with R-IVM group. All live births from R-IVM embryos were healthy and without malformations or complications. ConclusionR-IVM may improve the reproductive outcomes of women undergoing ICSI. It may also provide a reference for the safety of R-IVM. This study maybe support a routine application of R-IVM among patients who intend to undergo ICSI.