Conference Coverage
SAN DIEGO – The risk of thrombosis after giving birth remains significantly elevated for 12 weeks after delivery, twice as long as previously thought, an analysis of data on 1.7 million women found.
Dr. Hooman Kamel and his associates analyzed data on 1,687,930 million women admitted to nonfederal acute-care hospitals or emergency departments in California for first-time labor and delivery during 2005-2010, 1,015 of whom had a thrombotic event within 24 weeks after delivery (0.06%). These included strokes (248), MIs (47), and venous thromboemboli (720 cases).
The chance of a clotting event was 11-fold higher than normal in the first 6 weeks after delivery and was doubled when compared with normal in postpartum weeks 7-12, he reported in a press briefing at the International Stroke Conference.
An extra 22 cases/100,000 deliveries occurred in the first 6 weeks postpartum and an extra 3 cases per 100,000 deliveries occurred in weeks 7-12 postpartum.
By 13-18 weeks after delivery, a 40% higher odds of blood clot was not significantly different than with a year later, said Dr. Kamel, a neurologist at Cornell University, N.Y.
The blood clot risk returned to normal levels seen in women who’ve never delivered a baby by 19-24 weeks after delivery.
The New England Journal of Medicine published the findings online (2014 Feb. 13 [doi: 10.1056/NEJMoa1311485]).
The study confirms that thrombosis after delivery is rare and suggests that clinicians may want to take seriously any possible symptoms of stroke beyond the period that’s generally thought of as postpartum: 6 weeks after delivery. Especially in women who have other risk factors for thrombosis, awareness of continued elevated risk in weeks 7-12 could lead to quicker treatment if a blood clot forms, he said in an interview at the meeting, sponsored by the American Heart Association.
Current guidelines call for postpartum blood-thinning therapy in high-risk women who had an elevated stroke risk prior to pregnancy or other risk factors, and it’s unclear whether this should be extended beyond 6 weeks postpartum, Dr. Kamel said. The new findings may prompt research in this direction.
Meanwhile, physicians and women should take seriously any symptoms of possible thrombosis out to 12 weeks after delivery, such as chest pain or pressure, he said.
The study was supported by a grant from the National Institute of Neurological Disorders and Stroke. Dr. Kamel and his colleagues reported having no financial disclosures.
On Twitter @sherryboschert
Correction, 3/4/2014: An earlier version of this article misstated the amount of time passed between delivery and blood clot formation.