Objective: To investigate the correlation between different clinical features and live birth in patients with severe late-onset ovarian hyperstimulation syndrome (OHSS) after in vitro fertilization-embryo transfer (IVF-ET). Methods: The clinical information of 330 patients who were pregnant after IVF-ET and referred to medical treatments diagnosed as late-onset severe OHSS in Peking University Third Hospital from January 2016 to December 2020 was retrospectively analyzed. The patients were divided into live birth achieved group (n=287) and non-live birth achieved group (n=43) according to pregnancy outcomes, and live birth achieved group was further divided into two subgroups, full-term birth group (n=222) and early-term birth group (n=65) according to gestational week at delivery for better analysis. Single factor and multi-factor analysis were utilized to clarify the influencing factors of both live birth and early-term birth. Results: Among all the patients who received IVF-ET, the incidence of severe OHSS was 0.67% (673/100 758). Among 330 severe late-onset OHSS patients, 42.4% (140/330) had pleural effusion, the incidence of abnormal liver function was 69.4% (229/330), and the live birth rate was 87.0% (287/330). Among the 287 patients who achieved live birth, 55.4% (159/287) had no pleural effusion, 18.5% (53/287) had a small amount of pleural effusion, and 26.1% (75/287) had medium or massive pleural effusion; in the non-live birth achieved group, there were more patients without pleural effusion and less patients with a small amount of pleural effusion; the difference was statistically significant (χ2=6.213, P=0.045). The rate of selective fetal reduction in live birth achieved group was 16.0% (46/287), which was significantly higher than that in the non-live birth achieved group, which was 2.3% (1/43; χ2=5.749, P=0.017). Multivariate logistic regression analysis revealed that moderately abnormal liver function was an independent risk factor for live birth (OR=3.15, 95%CI: 1.60-6.19), while selective fetal reduction was an independent protective factor for live birth (OR=0.13, 95%CI: 0.02-0.96). Additionally, subgroup analysis suggested that twin birth was an independent risk factor for preterm birth (OR=8.54, 95%CI: 4.31-16.91). Conclusions: Moderate hepatic dysfunction may be associated with adverse pregnancy outcomes in patients with severe late-onset OHSS. Selective fetal reduction and singleton pregnancy are recommended to ameliorate live birth rate, full-term delivery rate, also the maternal and neonatal prognosis for patients with multiple pregnancies.