It’s well known that the risk of venous thromboembolism is increased during pregnancy. It is thought to be two-to-six times higher than the risk in non-pregnant women. However, these risk estimates are based on pregnant populations that go on to deliver a baby. Last year Ray et al. published a paper describing their findings on the unique risk of venous thromboembolism that exists after induced abortion.
The investigators identified 176,000 primigravid women whose first pregnancy ended in induced abortion and matched them with other women whose first pregnancy ended in delivery. They were also matched with non-pregnant controls. The primary outcome was any VTE within 42 days of abortion or delivery. They found that the risk was 30.1 per 100,000 after induced abortion, 184 per 100,000 after delivery, and 13.5 per 100,000 in the non pregnant group. In other words, induced abortion carries double the risk than that of non-pregnancy, but remains significantly lower than after a livebirth.
The risk of PE was 21 per 100,000 in the abortion group, and 125 in the livebirth group. There was no measurement or report of mortality in this study. However, we can look to the work by Greise et al. in 1978 which suggested that fatal PE is thought to occur in at least 1 out of every 350,000 women undergoing legal abortion (NOTE: this figure says nothing about temporality).
The implications of these findings are rather significant given that an estimated 25% of pregnancies worldwide end in abortion.
Liu N, Vigod SN, Farrugia MM, Urquia ML, Ray JG. Venous thromboembolism after induced abortion: a population-based, propensity-score-matched cohort study in Canada. Lancet Haematol. 2018;5(7):e279-e288.
Greiss FC Jr: Deaths caused by pulmonary thromboembolism after legally induced abortion. Discussion. Am J Obstet Gynecol 132:173, 1978