The chance of a woman developing a blood clot increases during pregnancy. Now, a new study has found that this risk remains higher than normal for at least 12 weeks after the birth - this is twice as long as previously thought.

"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," commented Dr Hooman Kamel of Weill Cornell Medical College in New York.

The study used data from 1.6 million women who gave birth in a US hospital between 2005 and 2010.

According to the researchers, the risk of a blood clot rises during pregnancy as platelets and other blood-clotting factors increase. This risk peaks around the time of the birth. However their study found that this risk remained almost 11 times higher in the six weeks after birth and 2.2 times higher between weeks seven and 12.

By weeks 19-24, the risk of a blood clot was back to what it would have been had the woman not had a baby.
The researchers noted that until now, the increased risk of a blood clot after having a baby was only thought to be around six weeks. They said that doctors should consider this when caring for ‘high-risk postpartum patients, such as those with previous clots, or postpartum patients with symptoms concerning for thrombosis'.

They also called on women themselves to be aware of the risk.

"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."

Details of these findings were presented at the American Stroke Association's International Stroke Conference 2014 in San Diego.

For more information on pregnancy, see our Pregnancy Clinic here