Hidden Risks for IVF Moms

Pregnant women using IVF appear at greater risk for blood clots and pulmonary embolism

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) As technology progresses, researchers must learn both the benefits and risks that new medical procedures offer. Using in vitro fertilization (IVF) to have a baby is one such technology.

IVF is a procedure in which a woman's egg is fertilized by sperm outside the woman's body in a lab. Then the egg is implanted in the woman to (hopefully) grow into a baby.

In a recent study, researchers found that pregnant women using IVF had a higher risk of blood clots than women who conceived naturally.

The overall risk of a blood clot was very low. About two to four of every 1,000 women will have one during pregnancy. The risk of a blood clot going to the lungs was even lower.

However, both these risks were a little higher among pregnant women who used IVF.

"Attend all prenatal visits."

The study, led by Peter Henriksson, a professor in the Division of Cardiovascular Medicine at the Karolinska Institutet's Danderyd Hospital in Sweden, looked at the rates of blood clots among pregnant women.

The initial group of participants included 23,498 women who had used in vitro fertilization (IVF) to get pregnant and then gave birth between 1990 and 2008.

Each of these women was then matched to five other women (total of 116,960 in the study) who were demographically similar but had natural pregnancies.

Then the researchers calculated the rate of pulmonary embolism and of venous thromboembolism in all the women. A pulmonary embolism is a blood clot in the lungs, and a venous thromboembolism is a blood clot in the veins that can travel to the lungs.

They found that 4.2 out of every 1,000 women who used IVF had blood clots in their veins, compared to 2.5 out of 1,000 women with natural pregnancies.

These rates put women with pregnancies conceived through IVF at a little under twice the risk for blood clots compared to women with natural pregnancies.

However, the overall risk of a blood clot for either group was still very low.

The researchers also found the first trimester to be the time period when women using IVF had the highest risk for developing clots compared to the second and third trimesters.

The rate for a blood clot in the veins during the first trimester was 1.5 out of 1,000 women using IVF versus 0.3 women out of every 1,000 (or 3 out of 10,000) with natural pregnancies.

The rates for getting a pulmonary embolism were also higher in the women with IVF, though a pulmonary embolism is still much rarer. Among the women who used IVF, 8.1 out of 10,000 had pulmonary embolisms, compared to 6 of 10,000 women with natural pregnancies.

This risk was also higher in the first trimester. While 3 women in 10,000 with IVF had pulmonary embolisms, 0.4 women in 10,000 women with natural pregnancies did.

The researchers therefore concluded that women using IVF were at a higher risk for blood clots and pulmonary embolism during their first trimester than women with pregnancies conceived naturally.

Again, however, the overall risk is still low.

"The risk of pulmonary embolism is low in absolute terms but because the condition is a leading cause of maternal mortality and clinical suspicion is critical for diagnosis, an awareness of this risk is important," the authors wrote.

The study was published January 15 in the journal BMJ. The research was funded by the Stockholm County Council, Karolinska Institutet and the Swedish Research Council. The authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
January 15, 2013
Last Updated:
January 15, 2013