Blood clot risk for women may last twice as long after pregnancy than once thought

A Filipina mother holds her baby boy after giving birth in the delivery room of the Fabella Maternity Hospital in Manila on New Year's day on Jan. 1, 2014. NOEL CELIS/AFP/Getty Images

Women may be at a higher risk for blood clots for at least 12 weeks after they give birth, according to new research.

The study, which was presented on Feb. 13 at the American Stroke Association’s International Stroke Conference in San Diego, doubles the amount of time that a woman was previously thought to be in danger of the life-threatening condition following pregnancy.

 “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,” Dr. Hooman Kamel, 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, said in a press release.

Blood clots may occur during pregnancy because platelets and other blood-clotting components increase in the body. Doctors sometimes give women blood thinners up to six weeks after delivery to lower the chance of the condition happening, the Associated Press reported.

Blood clots can cause additional health issues including blocking blood flow to the brain causing a stroke, and stopping blood flow to the heart -- a heart attack. The blood clot can travel to the lungs and get stuck causing a pulmonary embolism. It can also originate in the limb veins, travel throughout the body and block blood flow to other organs, which is called deep vein thrombosis.

The researchers used data on 1,687,930 women who had given birth between 2005 and 2010. Of them, 1,015 women had a blood clot within 1.5 years of giving birth.

The researchers determined that there was an almost 11 times higher risk of blood clots between zero to six weeks after giving birth. It dropped to a little over twice as high during weeks seven through 12.

During weeks 13 to 18, the risk was slightly elevated, but not enough to have a statistical difference over random chance. After week 19, the risk returned to normal.

Blood clots are rare, however: Fewer than one out of 10,000 women had a pregnancy-related blood clot six to 12 weeks after the baby was born.

If a woman experiences chest pain or pressure, problems with breathing, swelling or pain in one leg, severe and sudden headache or immediate loss of speech, vision, balance or strength on one side of the body, she may be having a blood clot-related issue. The researchers said women in these scenarios should contact a medical professional immediately.

The researchers encouraged doctors to make their pregnant patients aware of these risks, especially those who might be at a higher risk of having blood clots. This includes people with a previous history of clots or those who may have a increased chance of having deep vein thrombosis.

"Sometimes there's the notion that once they deliver they don't have to worry about these things," Dr. Andrew Stemer, a Georgetown University neurologist who was not involved in the study, told the AP.

The study was also published on Feb. 13 in the New England Journal of Medicine.

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