Women who undergo IVF have an increased risk of suffering blood clots while pregnant, a new study says
Swedish researchers found that a higher ratio of women who got pregnant following in vitro fertilisation ( IVF) suffered from venous thromboembolism (blood clots) than those who became pregnant naturally.
They found that 4.2 out of every 1,000 women who had IVF suffered blood clots compared with 2.5 of every 1,000 with natural pregnancies.
The researchers took data from 23,500 women who had IVF and 117,000 women with natural pregnancies.
The risk of pulmonary embolism - a potentially fatal blood clot which can prevent blood from reaching the lungs - in women who had the fertility treatment increased almost sevenfold during the first trimester of pregnancy, researchers said.
Infertility affects more than 10% of couples worldwide and to date about five million people have been born following IVF.
While it is known that the risk of blood clots is increased during pregnancy, researchers wanted to test whether there is an increased risk for women who undergo IVF.
They found that the risk after in vitro fertilisation increased during the whole pregnancy and differed between the trimesters. The risk was highest during the first trimester, researchers said.
The study, published on bmj.com, also found that a pulmonary embolism occurred in 8.1 women out of every 10,000 who have IVF, compared with six out of 10,000 who get pregnant naturally.
"Pregnant women are at higher risk of venous thromboembolism after in vitro fertilisation, particularly during the first trimester," the authors said.
"The risk of pulmonary embolism in women after in vitro fertilisation was increased almost sevenfold during the first trimester, although the absolute risk was low (two to three additional cases of pulmonary embolism per 10,000 pregnancies).
"Pulmonary embolism is, however, an elusive condition that is difficult to diagnose and is a leading cause of maternal death. Our finding is therefore important to health professionals dealing with women who are recently pregnant after in vitro fertilisation."
They added: "Doctors should be aware of these increased risks because the symptoms of pulmonary embolism can be insidious and the condition is potentially fatal."