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Women
who became pregnant through in vitro fertilization (IVF) may
have an increased risk of developing blood clots and
potentially fatal artery blockage, the researchers said.
Although the risk remains small, the odds are especially
high during the first trimester compared to women who become
pregnant naturally, investigators suggest. Blood clots,
called venous thromboembolism-can develop in the leg veins
and break free, traveling to the lungs and blocking a main
artery. This condition, called pulmonary embolism, can cause
difficulty breathing and even death. There is an increased
incidence of pulmonary embolism and venous thrombosis among
women pregnant after IVF, said lead researcher. Embolism is
the leading cause of maternal mortality during pregnancy.
The diagnosis can be elusive, so physicians should be aware
of this risk to facilitate the diagnosis. The risk of
clotting during pregnancy isn't confined to women who
undergo IVF, other experts said. Any pregnancy carries a
risk of clotting. This is because hormones, particularly
estrogen, increase during pregnancy. This changes the
clotting cascade. There are many factors in blood clotting
that can be affected by hormones-especially estrogen. In
addition, the enlarging uterus puts pressure on pelvic blood
vessels, which can lead to clotting. Although it's unclear
why women who undergo IVF have a greater risk of clotting.
Researcher speculates that it could be due to fertility
treatments that increase estrogen even beyond levels
normally associated with pregnancy. The genetics of women
who need IVF to conceive may also be a factor. For the
study, researchers compared data on more than 23,000 women
who became pregnant after IVF with nearly 117,000 women who
conceived without assisted technology. Researchers found
that for women who had undergone IVF, the risk for a blood
clot was 4.2 in 1,000 women. For the women with normal
pregnancies, the risk was 2.5 in 1,000. Moreover, the risk
was highest during the first trimester. Pulmonary embolism
occurred in 19 women who had IVF (8.1 out of 10,000)
compared with 70 women who conceived normally (6.0 out of
10,000), the study found. Investigators caution that the
absolute risk of a pulmonary embolism among women who had
IVF was still slight two to three additional cases in 10,000
women. Also, most blood clots do not go to the lungs and can
easily be treated and resolved. Women at risk for clots can
be treated with blood thinners that prevent clots,
researcher said. |