REPOST: A rise in pregnancy clots

What is venous thrombosis and how risky it is for pregnant women? This New York Times article has the answer.

Pregnancy increases the risk of venous thrombosis, which involves blood clots in the veins, and pulmonary embolism, a blood clot in the arteries of the lungs that can be fatal. The absolute risk is low — about one in a thousand over an entire pregnancy. But a new study suggests that both kinds of clots may be more common in pregnancies achieved by in vitro fertilization.

Swedish researchers compared 23,498 women who had given birth after I.V.F. from 1990 to 2008 with 116,960 women of the same age and general health who had natural pregnancies. The results appeared online last week in the journal BMJ.

Women with I.V.F. pregnancies had more than four times the risk of venous thrombosis during the first trimester, compared with those with natural pregnancies, and almost seven times the risk of pulmonary embolism. The difference narrowed, but persisted, as the pregnancies progressed.

The I.V.F. procedure induces multiple egg production with high doses of hormones, and the authors suggest that this may be the cause.

“Women who are going to have I.V.F. should know these findings,” said the lead author, Dr. Peter Henriksson, a professor of internal medicine at the Karolinska Institute. “And if they have had blood clots themselves, or have relatives with thrombosis, they should be treated with blood thinners.

Cristian Andronic has more than 12 years of experience in the field of obstetrics and gynecology. Follow this Twitter page for more updates.