LAUSR

BACKGROUND  Since venous thromboembolism (VTE) is one of the causes of maternal mortality, several guidelines recommend prophylaxis using low molecular weight heparin for women in high-risk groups. The number of large population-based studies examining predictors for VTE has been limited, and there has been no study based on a Japanese population. OBJECTIVE  Our objective was to examine VTE risk factor during the pregnancy and post-partum period. MATERIALS AND METHODS  A nationwide birth cohort study known as the 'Japan Environment and Children's Study (JECS)' was conducted by the Ministry of the Environment. The subjects consisted of 103,070 pregnancies recruited by the JECS between January 2011 and March 2014. Pregnant women completed the questionnaires during the first and second/third trimester. Their medical records were transcribed by physicians or research coordinators at registration, just after delivery and at 1 month after delivery. RESULTS  The frequency of VTE was 7.5 per 10,000 pregnancies (77 of 103,070) during the pregnancy and post-partum period. After the adjustment of multiple covariates for each factor, endometriosis and recurrent pregnancy loss (RPL) were identified as novel independent risk factors for VTE. Adjusted odds ratios were as follows: 2.70 (95% confidence interval, 1.21-6.00) for endometriosis and 6.13 (2.48-15.16) for RPL. Threatened abortion, threatened pre-term birth, pre-term birth and caesarean section were ascertained to be risk factors for VTE. CONCLUSION  Careful attention should be given to novel predictors, such as endometriosis and a history of RPL, to prevent VTE during the pregnancy and post-partum period.