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). 

Kamel H, Navi BB, Sriram N, Hovsepian DA, Devereux RB, Elkind MS. Risk of a Thrombotic Event after the 6-Week Postpartum Period. N Engl J Med. 2014 Feb 13. [Epub ahead of print]