A retrospective cohort study using a national surveillance questionnaire to investigate the characteristics of maternal venous thromboembolism in Japan in 2018

BACKGROUND: In Japan, the numbers of deliveries by women of older maternal age and women with overweight or obesity have recently increased. Since 2008, the guidelines and practices to prevent the maternal venous thromboembolism (VTE) have been recommended antepartum and postpartum thromboprophylaxis for each risk level of VTE. This study aimed to clarify the incidence and characteristics (type of VTE and thromboprophylaxis) of 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. RESULTS: At the responding institutions, 243 women (0.082%) had VTE in 2018. In 2018, 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). The incidence of VTE after cesarean Sect. (0.0074%) was significantly higher than that after vaginal delivery (0.0012%; p < 0.0001). Of the women with VTE, 4 (1.6%) died. CONCLUSIONS: Among the women thought to have a low risk of VTE during the antepartum period, and especially women who had a vaginal delivery, the actual incidence of VTE might have increased in Japan. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-021-03993-1.