Results
Study population and characteristics
A total of 129443 women gave birth in Shanghai First Maternity and Infant Hospital between January 1st, 2017 and July 31th, 2021 and 151 (11.7 per 10000) women experienced VTE in pregnancy or in the first 6 postnatal weeks. Of these, 65.6% (99 of 151) was PE alone and 34.4% (52 of 151) was DVT alone or combined with PE. 302 women who did not experience a VTE were selected as control. The prevalence of known risk factors for VTE was significantly higher in cases than controls (Table 1). In particular, cases were more likely to be of advanced age (23.2% versus 14.3%), to be overweight or obese (19.3% versus 11.0%), to have multiple birth (6.6% versus 2.7%), pregnancy-induced hypertension (PIH) (17.9% versus 6.0%), hypothyroidism (9.3% versus 3.7%), preterm birth (17.3% versus 5.0%), postpartum hemorrhage (14.6% versus 5.0%), abruptio placentae (4.0% versus 1.0%), ischemic placental diseases (26.5% versus 12.0%), delivery via cesarean delivery (81.5% versus 46.3%), newborns with low birth weight (15.2% versus 4.3%) and respiratory distress syndrome (6.6% versus 1.7%).