As you know, pregnancy increases the risk of thrombosis. This risk is even higher postpartum (within 6 weeks after giving birth). Relative to the nonpregnant state, the 6 week postpartum period has been associated with 3-9 times risk of stroke, 3-6 times risk of MI, and 9-22 times risk of venous thromboembolism (VTE).
Risk factors for postpartum thrombosis: (1) Maternal age > 35 years (2) Primary hypercoagulable state (3) Eclampsia or preeclampsia (4) Smoking (5) Cesarean delivery
A recent article in NEJM has suggested an increased risk of thrombosis up to 12 weeks postpartum. But an absolute increase in risk beyond 6 weeks postpartum was found to be low.
Here are the highlights from the must read article.
- Crossover-cohort study of 1,687,930 G1P1 women of whom 1015 had a thrombotic event (248 strokes, 47 MI’s, 720 VTE’s) within 24 weeks postpartum.
- 411 thrombotic event within 6 weeks postpartum compared to 38 events during same period 1 year later; absolute risk difference of 22.1 events per 10,000 deliveries (95% confidence interval [CI], 19.6 to 24.6); odds ratio of 10.8 (95% CI, 7.8 to 15.1)
- 95 thrombotic events within 7-12 weeks postpartum compared to 44 events during same period 1 year later; absolute risk difference of 3.0 events per 100,000 deliveries (95% CI, 1.6 to 4.5); odds ratio of 2.2 (95% CI, 1.5 to 3.1)
- No significant increase in risk of thrombotic events beyond 12 weeks postpartum
If you do diagnose VTE postpartum, remember you can start anticoagulation 6 hrs after vaginal delivery and 12 hrs after cesarean section (as long as the delivery was not too traumatic).