Women with preeclampsia/eclampsia and postpartum acute systemic infection experienced the greatest risk for developing venous thromboembolism during the first 3 weeks postpartum, according to study results.
Alyshah Abdul Sultan, PhD, of the division of epidemiology and public health at the University of Nottingham, and colleagues evaluated data from 168,077 women who had 222,334 pregnancies between 1997 and 2010. Researchers identified 178 cases of venous thromboembolism (VTE) in the study population during the postpartum period.
The risk for VTE was greatest in the first 3 weeks postpartum among women with preeclampsia/eclampsia (incidence rate ratio [IRR]=2.54; 95% CI, 1.23-5.26) and in women who experienced postpartum acute systemic infection (IRR=5.99; 95% CI, 3.36-10.6). These risks for VTE persisted to a lesser degree 4 to 6 weeks postpartum (preeclampsia/eclampsia, IRR=5.41; 95% CI, 1.84-15.8; acute systemic infection, IRR=3.56; 95% CI, 1.08-11.7).
BMI ≥30 also was associated with an increased risk for VTE 1 to 3 weeks (IRR=2.74; 95% CI, 1.66-4.51) and 4 to 6 weeks (IRR=4.18; 95% CI, 1.65-10.5) postpartum.
Women who underwent cesarean section demonstrated an increased risk for VTE 1 to 3 weeks postpartum (IRR=1.89; 95% CI, 1.3-2.74) and 4 to 6 weeks postpartum (IRR=6.99; 95% CI, 3.07-15.9).
Pre-term birth (absolute rate per 100,000 pregnancies [AR]=119; 95% CI, 73-183) and postpartum hemorrhage (AR=122; 95% CI, 78-181) were associated with an increased risk for VTE only 1 to 3 weeks postpartum.
Researchers calculated a number needed to treat based on a 50% risk reduction of 1,173 for women with infection and 1,289 for women with preeclampsia/eclampsia during the first 3 weeks postpartum. The number needed to treat increased to 5,090 for women with infection and to 2,557 for women with preeclampsia/eclampsia 4 to 6 weeks postpartum.
“Recommendations regarding postpartum thromboprophylaxis with low–molecular-weight heparin for women with [these] risk factors will of course be highly dependent on the combination of the risk reduction from prophylaxis and any adverse events from its use, both of which were beyond the scope of this study,” Sultan and colleagues concluded. “Nevertheless our study provides the most robust, comprehensive and clinically relevant information on risk factors for postpartum VTE that can be of direct use in formulating such guidelines.”
Disclosure: One researcher received honoraria from Leo Pharma and Sanofi, and also was a co-developer of current guidelines for VTE prophylaxis during pregnancy issued by the Royal College of Obstetricians and Gynecologists.