Hormonal exposure leads to an increased risk of venous thromboembolism (VTE) but the risk of VTE associated with assisted reproductive technology (ART) is not clearly determined.We searched in PubMed, EMBASE, Web of Science, and the Cochrane Library databases and identified all relevant articles published up to February 1, 2021.The primary objective was to determine the frequency of VTE associated with ART. Secondary objectives were to determine (1) the risk of VTE associated with ART as compared to pregnancy without ART; (2) the risk of VTE associated with ovarian hyperstimulation syndrome (OHSS); and (3) to determine potential risk factors of VTE related to ART.Fourteen studies were included. The overall frequency of VTE associated with ART was 0.23% (95% confidence interval [CI]: 0.07–0.46). Women undergoing ART had a two- to threefold increased risk of VTE as compared to spontaneous pregnancy (relative risk [RR]: 2.66; 95% CI: 1.60–4.43). The overall frequency of VTE specifically related to OHSS was <0.001%. The risk of VTE after ART complicated by OHSS, as compared to ART without OHSS, was higher but not statistically significant (RR: 14.83; 95% CI: 0.86–255.62). Risk factors of VTE associated with ART were in vitro fertilization procedure (RR, odds ratio [OR], and hazard ratio varying from 1.77, 95% CI: 1.41–2.23 to 4.99, 95% CI: 1.24–20.05), hyperhomocysteinemia (OR: 15.2; 95% CI: 2.0–115.0), polycystic ovarian syndrome (PCOS) (RR: 4.8; 95% CI: 1.7–13.4), successful ART leading to pregnancy (OR: 13.94; 95% CI: 1.41–137.45).Further large prospective studies on risk factors of VTE in women undergoing ART are needed in order to optimize thromboprophylaxis in this context.

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Background: Women with a previous venous thromboembolism (VTE) are at risk of recurrence during pregnancy.Objectives: We aimed to assess the incidence rate of recurrent VTE during pregnancy, according to the period of pregnancy, and the clinical parameters associated with recurrence, in a prospective cohort of women of childbearing age after a first VTE.Patients/Methods: A total of 189 women aged 15-49 years with a first documented VTE were followed until a subsequent pregnancy of at least 20 weeks' gestation between 2000 and 2020. VTE recurrences during pregnancy were recorded, as were potential clinical risk factors for recurrence. Results: Recurrent VTE occurred in six women during antepartum: five during the first trimester (incidence rate 106.4 per 1000 women-years) (95% confidence interval [CI] 46.3-226.0); none during the second trimester; and one during the third trimester (incidence rate 27.0 per 1000 women-years [95% CI 4.8-138.2]). During postpartum, recurrences occurred in 11 women (incidence rate 212.8 per 1000 women-years [95% CI 119.9-349.1]). These 17 recurrent VTEs presented as pulmonary embolism ± deep vein thrombosis (DVT) in five patients and isolated DVT in 12. Failure of thromboprophylaxis occurred in two cases (33.3%) antepartum and in 10 cases (90.9%) postpartum.In multivariable analysis, only obesity (defined on prepregnancy body mass index) was associated with recurrent VTE (odds ratio 3.34 [95% CI 1.11-10.05, p = .03]). Conclusions:This study confirms a high risk of recurrent VTE postpartum, despite thromboprophylaxis, in women with a previous VTE. Only obesity was associated with VTE recurrence during pregnancy, suggesting that low-dose anticoagulation might not be appropriate in obese pregnant women.