Hypertension during pregnancy, pre-eclampsia up risk of venous thromboembolism

Pregnant women with hypertension during pregnancy or pre-eclampsia are at greater odds of developing venous thromboembolism (VTE) both on the short and long term after pregnancy, a study has found.

Researchers followed of 1,919,918 women with at least one pregnancy for a median of 13.7 years for a total of 24,531,118 person-years. A total of 5,759 first VTEs occurred, yielding an incidence rate of 2.3 (95 percent confidence interval [CI], 2.3–2.4) per 10,000 person-years.

In the cohort, 1,624,849 women (84.6 percent) had uncomplicated pregnancies (reference group), 264,135 (13.8 percent) had ≥1 pregnancies complicated by hypertension, and 30,934 (1.6 percent) had ≥1 pregnancies complicated by pre-eclampsia. The mean age at the start of follow-up was similar among groups at about 29 years.

In Cox proportional hazard models, VTE risk was twofold higher among women with hypertension (hazard ratio [HR], 2.0, 95 percent CI, 1.7–2.4) and about eightfold increased among women with pre-eclampsia (HR, 7.8, 95 percent CI, 5.4–11.3) as compared with the reference group.

On the long term, women in both the hypertension and pre-eclampsia groups were likewise at greater odds of developing VTE (vs the reference group: HR, 1.5, 95 percent CI, 1.4–1.6 and HR, 2.1, 95 percent CI, 1.8–2.4, respectively). Risk estimates were attenuated after excluding events during pregnancy and postpartum (HR, 1.4, 95 percent CI, 1.3–1.5 and HR, 1.6, 95 percent CI, 1.4–2.0, respectively).

The present data suggest that while the hypertensive disorders are transient and end with delivery of the placenta, the risk of VTE remains high in the following years, the researchers said. This follows that “hypertensive disorders of pregnancy and pre-eclampsia in particular are associated with persistent underlying, currently unknown, risk factors.”