A history of endometriosis and recurrent pregnancy loss (RPL) were identified as novel risk factors for venous thromboembolism (VTE) during pregnancy and the postpartum period in a recent study published in Thrombosis and Haemostasis.

Pregnancy and postpartum are associated with developing VTE, so guidelines recommend thromboprophylaxis with low-molecular-weight heparin for high-risk patients. Previous research indicates prior VTE is the highest risk factor for VTE in pregnancy or postpartum.

Researchers aimed to evaluate risk factors for VTE during pregnancy and postpartum in a Japanese population and to expand the research on this risk in a large, population-based study.

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In this study, researchers in Japan used the Japan Environment and Children’s Study (JECS), a nationwide birth cohort consisting of 103,070 pregnant women enrolled between January 2011 and March 2014. Subjects completed questionnaires on sociodemographic characteristics, medical history, details of all prior pregnancies, exercise habits, income, and education level. The questionnaires were administered in 2 stages; the first during the first trimester and the second in the second or third trimester. Medical records were transcribed at registration into the cohort, just after delivery, and 1 month after delivery.

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The frequency of VTE was found to be 7.5 per 10,000 pregnancies. After adjusting for multiple covariates, a history of endometriosis and RPL were identified as novel, independent risk factors for VTE. The adjusted odds ratio for endometriosis was 2.70 (95% confidence interval [CI], 1.21-6.00; P =.015). The adjusted odds ratio for RPL was 6.13 (95% CI, 2.48-15.16; P <.001).

Preterm birth, caesarean section, threatened preterm birth, and threated abortion were also found to be risk factors for VTE.

“Consequently, we should pay careful attention to novel predictors, such as endometriosis and RPL, to prevent VTE in pregnant women,” concluded the authors.


1. Sugiura-Ogasawara M, Ebara T, Matsuki T, et al. Endometriosis and recurrent pregnancy loss as new risk factors for venous thromboembolism during pregnancy and post-partum: The JECS birth cohort [published online February 5, 2019]. Thromb Haemost. doi: 10.1055/s-0039-1677733