2.1. Data sources
This cross-sectional survey collected data on thromboembolism in pregnancy from January 1 to December 31, 2019. Participating hospitals included those across all levels that provided maternal healthcare services in mainland China. Based on the Chinese national network of women’s and children’s health, a survey request was sent to the chief of the Department of Obstetrics of each hospital. Hospitals that completed the survey and signed informed consent before February 29, 2020 were enrolled for the final analysis, and those with missing data were excluded. The Institutional Review Board of the Obstetrics and Gynecology Hospital of Fudan University approved the project, and written informed consent was obtained from each participating hospital before enrollment.