Previous studies focused on the first six weeks after delivery
An increased risk of having a stroke or other blood-clotting problem could last as long as 12 weeks after childbirth, twice as long as previously thought, according to a new study.
“We found the risk of blood clots remained higher than normal for twice as long as previously thought. After 12 weeks, it was no longer significant,” says Hooman Kamel, M.D., an assistant professor in the Weill Cornell Medical College department of neurology and the study’s lead author. “Historically, six weeks was the accepted period.”
Researchers looked at medical information from nearly 1.7 million California women who had delivered their first child. Through 18 months after delivery, about 1,000 of the women had clotting problems, including 250 strokes, 50 heart attacks and more than 700 cases of clots in the legs or lungs.
“We found the risk of these types of blood clots during the first six weeks after birth was [more than] 10 times higher than normal,” Dr. Kamel says. In the seven to 12 weeks following delivery, the risk remained elevated, but dropped to twice the normal rate.
According to the American Society of Hematology, blood clots form more easily during pregnancy, with the risk of clotting problems higher in women who are obese, smoke, have high blood pressure, are largely sedentary, or have a family history of clots. Women on prolonged bed rest or who take long plane or car trips while pregnant are also at an increased risk.
Currently, doctors prescribe low-dose blood thinners to high-risk women for six weeks after delivery to reduce their risk. This new research may make health-care professionals rethink the timeframe for medication.
The risk of stroke or clots following childbirth is low, but Dr. Kamel stresses the importance of recognizing the warning signs of a blood clot: chest pain or pressure; difficulty breathing; pain or swelling in one leg; sudden, severe headache; or sudden change in consciousness, speech, balance, strength or sensation on one side of the body.