Characteristics of Maternal Venous Thromboembolism in Japan, 2018: A Retrospective Cohort Study with National Surveillance Questionnaire Conducted in Maternity Hospitals

Background: In Japan, deliveries by women of older maternal age and by women with overweight or obesity have recently increased. While, since 2008, the guidelines and practices to prevent the maternal VTE have been recommended. This study aims to clarify the incidence and characteristics of venous thromboembolism (VTE) in pregnant women in Japan to reduce the rate of mortality from VTE.Methods: Of 2299 institutions sent the surveillance questionnaire, 666 (29.0%) responded, and data from 295,961 women who gave birth in those institutions in 2018 were analyzed. We calculated the incidence and characteristics of VTE before and after the deliveries in the three types of institutions (perinatal medical centers, general hospital with obstetric facilities, and maternal clinic with beds). To clarify the incidence and characteristics of VTE, and to clarify the relationship between the incidence of the VTE and the types of institutions in 2018 in Japan.Results: At the responding institutions, 20 (0.0068%) died, and 243 women (0.082%) had VTE. Deep vein thrombosis was significantly more common (0.0053%) than pulmonary thromboembolism (0.0019%; p < 0.0001). The incidence of antepartum VTE (0.0055%) was significantly higher than that of postpartum VTE (0.0026%; p < 0.0001). Among the 165 women with antepartum VTE, perioperative pulmonary thromboembolism (30.0%) was more common than perioperative deep vein thrombosis (8.8%, p = 0.0150). The incidence of VTE after cesarean section (0.0074%) was significantly higher than that after vaginal delivery (0.0012%; p < 0.0001). After cesarean section, the incidence of pulmonary thromboembolism (46.4%) was significantly higher than that of deep vein thrombosis (10.8%; p < 0.0001). Of the women with VTE, four (1.6%) died.Conclusions: Obstetricians should be strongly encouraged to administer thromboprophylaxis to decrease the incidence of VTE because among women thought to have low risk of VTE, the incidence might have increased in Japan.