Blood Clots After IVF

Women sometimes develop blood clots in their veins (venous thromboembolism) or pulmonary arteries (pulmonary embolism) during pregnancy.   The development of blood clots during normal pregnancy is a rare event, but when it occurs but it can be potentially serious.

Women who are contemplating IVF (in vitro fertilization) should be aware that according to a recent report, the risks of developing venous blood clots during an IVF-induced pregnancy are about 77% higher than during a normal pregnancy.   The risk is especially increased during the first trimester. However, the absolute risk is still fairly low; about 4.2 cases per 1,000 pregnancies.  It’s nothing to worry about unduly, but perhaps it’s something that should be discussed with one’s doctor before undergoing IVF.

The authors hypothesize that perhaps the reason for the increased risk is that high doses of estrogen generally are used to stimulate egg development prior to egg collection in an IVF procedure.   Exogenous estrogen (in birth control pills or in hormone replacement therapies after menopause) is known to be associated with venous thromboembolism.   This raises an interesting untested question – would women who undergo an IVF procedure but who do not become pregnant also be at increased risk for blood clots?  As far as I know, that has never been tested.