The Incidence of Moderate and Severe Ovarian Hyperstimulation Syndrome in Hospitalized Patients in China.

Background: Ovarian hyperstimulation syndrome (OHSS) occurs in women receiving fertility treatments. Moderate and severe OHSS cases are required to be admitted to hospital for treatment. The incidence of moderate and severe OHSS and the characteristics of these cases are unknown in China. We aimed to assess the incidence of moderate and severe OHSS in national databases from China between 2013 and 2017. Methods: We extracted moderate and severe OHSS cases from the Hospital Quality Monitoring System, the nationwide inpatient data collection system. We used ovum pick-up (OPUbaidu) cycle data from the annual report of China's National Health Commission, developed on the basis of OPU data collected by National ART Management Information System. Overall incidence of moderate and severe OHSS (women aged 20 to 50 years) and year-specific incidence by each calendar year in China were calculated. We also investigated the age distribution in OHSS and OHSS with different comorbidities. Results: We extracted 18,022 eligible patients with moderate or severe OHSS and 1,581,703 OPU cycles. The overall incidence of moderate and severe OHSS between 2013 and 2017 was 1.14%. The year-specific moderate and severe OHSS incidence was 1.1% in 2013, 1.4% in 2014, 1.4% in 2015, 1.1% in 2016, 0.9% in 2017, respectively. Women aged 26 to 30 years accounted for 48.4% of OHSS cases, followed by women aged 31 to 35 years (30%) and 20 to 25 years (14.2%). The age distribution pattern was consistent across OHSS with different comorbidities. Conclusions: This study reported the incidence of moderate and severe OHSS in China using nationwide data for the first time. Our findings support that women aged under 35 years receiving assisted reproductive technology need more attention than other age groups in terms of OHSS risk control.