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Risk for thrombotic events may persist for 12 weeks after delivery
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SAN DIEGO — Findings from a new study suggest that elevated risk for thrombosis persists in new mothers until 12 weeks after delivery; however, the absolute increase in risk beyond 6 weeks after delivery was low.
Hooman Kamel, MD, of Weill Cornell Medical College, New York, and colleagues used California medical databases to identify women hospitalized for labor and delivery from January 2005 to June 2010 (n=1,687,930), and then to identify which women had ischemic stroke, acute MI or venous thromboembolism. The researchers analyzed each woman’s likelihood of a first thrombotic event during sequential 6-week periods after delivery as compared with the corresponding 6-week period 1 year later.
In total, 1,015 thrombotic events occurred (stroke, 248; MI, 47; venous thromboembolism, 720) during the study period.
The researchers observed elevated risk for thrombotic events in the first 6 weeks after delivery (411 events vs. 38 events; absolute risk difference, 22.1 events per 100,000 deliveries; OR=10.8; 95% CI, 7.8-15.1), compared with the corresponding 6-week period 1 year after delivery, according to Kamel.
In addition, the study revealed a smaller increased risk for thrombotic events seven to 12 weeks after delivery, compared with the 7- to 12-week period 1 year after delivery (95 events vs. 44 events; absolute risk difference, 3 events per 100,000 deliveries; OR=2.2; 95% CI, 1.5-3.1).
“That’s lower than during the first 6 weeks, but significantly higher than usual,” Kamel said at a press conference. “The risk of thrombosis after delivery has a tapering course, and seems to return to normal somewhere in the 13- to 18-week period.”
The researchers found no evidence of elevated risk beyond week 12 post-delivery.
“This suggests potential avenues for future studies of some patients who are at very high baseline risk, for example, patients who have had a blood clot before pregnancy,” Kamel said. “Current guidelines recommend low-dose blood thinners for the first 6 weeks after pregnancy. Perhaps future studies can look at whether a longer duration of treatment is beneficial.” – by Erik Swain
For more information:
Kamel H. Abstract #216. Presented at: International Stroke Conference 2014; Feb. 12-14, 2014; San Diego.
Kamel H. N Engl J Med. 2014;doi:10.1056/NEJMoa140213.
Disclosure: Kamel reports no relevant financial disclosures.
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Bruce Ovbiagele, MD, MSc, MAS
The biggest issue identified by the study is that of sustained risk beyond 6 weeks. That is one of the reasons why I think it informs clinical practice, because traditionally, and arbitrarily, we had this 6-week postpartum period where we were surveilling these individuals for thrombolic events, but now we know that it extends, albeit at a lesser risk, up to 12 weeks. So, surveilling these individuals, and potentially even extending anticoagulation or antithrombosis therapies, in that period might be considered. We need more information, and I know Dr. Kamel is going to further analyze this issue. But it’s important that we now know that that risk doesn’t go back to normal after 6 weeks. It is still sustained, albeit at a less-high rate.
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Michael R. Jaff, DO
Pregnancy and the immediate postpartum period are known to carry increased risk for thromboembolic events. Most consider 6 weeks following delivery as the risk period. Kamel et al used a California administrative database to assess the actual risk of postpartum thromboemboli. In reviewing 648,148 women who suffered a thromboembolic event, either arterial or venous, they found that 1,620 had delivered a baby within the prior 24 weeks. As expected, the postpartum risk was highest within the first 6 weeks of delivery. However, the odds of having a thromboembolic event remained greater than two times that of normal up to 12 weeks following delivery.
This has important clinical relevance, as physicians must maintain a heightened sense of awareness when postpartum women present with symptoms which may be suggestive of thromboemboli, even out to 12 weeks following delivery.
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