News Release

Blood clot risk remains higher than normal for at least 12 weeks after women deliver babies

Abstract: 216 (Room Hall E)

Peer-Reviewed Publication

American Heart Association

Women's blood clot risk remains elevated for at least 12 weeks after delivering a baby — twice as long as previously recognized, according to a large study presented at the American Stroke Association's International Stroke Conference 2014.

The chance of a blood clot rises during pregnancy, when platelets and other blood-clotting factors increase. The risk peaks around the time of delivery, but researchers found that afterwards it remained:

  • 10.8 times higher during weeks 0-6;

  • 2.2 times higher during weeks 7-12; and

  • 1.4 times higher (a non-significant rise) during weeks 13-18.

By weeks 19-24, the chance of a blood clot returned to what it would have been if a woman had not delivered a baby.

Fewer than one in 10,000 women suffer a pregnancy-related blood clot six to 12 weeks after delivery.

"While rare, blood clots are a serious cause of disability and death in pregnant and post-partum women, and many members of our research team have cared for young women with these complications," said Hooman Kamel, M.D., lead researcher and assistant professor in the Department of Neurology and the Brain and Mind Research Institute of Weill Cornell Medical College in New York City.

"If you have recently delivered a baby, seek medical attention if you develop symptoms such as: chest pain or pressure; difficulty breathing; swelling or pain in one leg; sudden severe headache; or sudden loss of speech, vision, balance, or strength on one side of your body."

The researchers calculated the odds using data on 1,687,930 women admitted for labor and delivery at a California hospital in 2005-10. Of those, 1,015 women had a clot during the following 1.5 years. These included women with clots that interrupted blood flow in the brain (stroke), heart (heart attack), lungs (pulmonary embolism) or limbs (deep vein thrombosis).

"Clinicians should consider our results when caring for high-risk postpartum patients, such as those with previous clots, or postpartum patients with symptoms concerning for thrombosis," Kamel said.

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Co-authors are: Babak B. Navi, M.D.; Nandita Sriram, B.S.; Dominic A. Hovsepian, B.S.; and Mitchell S.V. Elkind, M.D., M.S. Author disclosures are on the abstract.

The National Institute of Neurological Disorders and Stroke funded the study.

Downloadable video/audio interviews, B-roll, animation and images related to this news release are on the right column of the release link located at http://newsroom.heart.org/news/blood-clot-risk-remains-higher-than-normal-for-at-least-12-weeks-after-women-deliver-babies?preview=32a51662d96af924d25afee05a82122a. Video clips with researchers/authors of the studies will be added to the release links after embargo.

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Get additional information on:

  • Pregnancy and stroke

  • Women's stroke risks

Statements and conclusions of study authors that are presented at American Stroke Association scientific meetings are solely those of the study authors and do not necessarily reflect association policy or position. The association makes no representation or warranty as to their accuracy or reliability. The association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific association programs and events. The association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and device corporations are available at http://www.heart.org/corporatefunding.

Note: Actual presentation is 11:24 a.m.PT on Thursday, Feb. 13, 2014.


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