Trends, risk factors and mortality among women with venous thromboembolism during labour and delivery: a population-based study of 8 million births

Venous thromboembolism (VTE) is amongst the main causes of maternal death in the developed world. The objective of this study is to elucidate risk factors of VTE and specifically, predictors of fatal thromboembolic disease during the delivery. We conducted a population-based cohort study on 8 million birth records using the Healthcare Cost and Utilisation Project-Nationwide Inpatient Sample from 1999 to 2008 to estimate the incidence and case fatality of VTE's during labour admission. Logistic regression was used to calculate the odds ratio (OR) and corresponding 95 % confidence intervals (CIs) of demographic and obstetrical determinants of VTEs and fatal VTEs. The overall incidence of VTE was 167.7/100,000 births, increasing over the 10-year period, with an average case fatality rate of 0.41 %. VTE was associated with maternal age above 25, elderly primigravida, multigravida, black race, smoking, thrombophilia, cardiovascular disease, hypertension, obesity, postpartum haemorrhage and blood transfusion. Predictors of VTE fatalities included black race, hypertension, caesarean section and transfusion. VTE is a rare but serious condition that is increasing in incidence and is associated with a significant degree of maternal morbidity and mortality. Further research targeting prevention among high-risk groups is warranted.