In vitro fertilization (IVF) is linked to an elevated risk of pulmonary embolism (blockage of the lung’s principal artery) and venous thromboembolism (blood clots) during the 1st trimester of pregnancy.

The finding came from new research conducted by the Karolinska Institute in Sweden and published in British Medical Journal.

About 10% of couples are affected by infertility around the world; since 1978, they have been able to use IVF to help them get pregnant. To date, IVF has contributed to an estimated 5 million births

Scientists have been aware that the risk of blood clots becomes greater during normal pregnancy, about 1 in 1000 pregnant women developed them in the early 1990s. A recent study demonstrated that women who are pregnant and women who have given birth within the past 3 months are four times as likely to have “serious blood clot problems”.

IVF pregnancies have been found to cause more blood clots than normal pregnancies. However, the risk of artery blockage following IVF is not known, which is significant because it commonly causes maternal deaths.

As a result, the team of experts set out to compare the risk of both pulmonary embolism (PE) and venous thromboembolism (VTE) in 23,498 females going through an IVF pregnancy and 116,960 females going through a normal pregnancy.

The women analyzed were 33 years old on average; all gave birth between 1990 and 2008. More women in the IVF group experienced blood clots than those in the normal pregnancy group (4.2 in 1000 vs. 2.5 in 1000).

During the first trimester, the chance of developing blood clots increased (1.5 in IVF group and 0.3 in unexposed group).

The researchers found no dissimilarity in risk before pregnancy or during the year after giving birth.

PE was recognized in 19 females in the exposed group (0.08%) and 70 females in the normal pregnancy group (0.05%). The IVF group experienced an increase in the risk of PE during the whole pregnancy, but especially during the 1st trimester.

Although absolute risks for PE was low, the scientists explained, there were 2 to 3 extra cases per 10,000 IVF females. However, it is challenging to diagnose PE and it is still a main cause of maternal death, making these results significant to doctors.

The experts found the same results even after taking certain factors into account, including:

  • BMI
  • maternal age
  • calendar years of delivery
  • smoking
  • family situation
  • education
  • country of birth
  • parity

The authors concluded that after IVF, there is an elevated chance of blood clots, and significantly, an increased risk of artery blockage in pregnancy.

Since it is a condition that could potentially lead to death, the team noted that all doctors should be aware of these findings. They recommended that “efforts should focus on the identification of women at risk”.

Written by Sarah Glynn