New research on blood thinner use in pregnancy

Blood-thinning medications taken during pregnancy do not reduce adverse pregnancy outcomes, like blood clots, placenta-mediated pregnancy complications or pregnancy loss, a new study has found.

“Women are at higher risk of developing blood clots during pregnancy, especially those with thrombophilia. Those who have previously experienced blood clots or unexplained pregnancy loss have been increasingly treated with dalteparin, an anticoagulant medication that thins the blood. However, there was no strong evidence to show with certainty whether or not this course of treatment was beneficial, ” says Dr. Anne McLeod, hematologist at Sunnybrook Health Sciences Centre and a co-investigator of the study.

Led by the University of Ottawa’s Dr. Mark Rodger, the Thrombophilia in Pregnancy Prophylaxis Study (TIPPS), published today in The Lancet, is the first large international randomized controlled trial of its kind. It included 292 women with thrombophilia who had experienced previous pregnancy complications or loss, recruited over 12 years.

Approximately half of the women in the trial received dalteparin injections during pregnancy, while the other half did not. Researchers found no difference between the two groups in terms of adverse pregnancy outcomes, such as venous thromboembolism, pre-eclampsia, small-for-gestational-age infants, placental abruption, or pregnancy loss.

Dr. McLeod anticipates the findings of the study will be practice changing. “For women who have wanted to try something to avoid another adverse outcome, injecting dalteparin can require up to 400 shots during the pregnancy, a significant commitment. We want to help our patients, but at the same time, we want to ensure the evidence is there to support the course of treatment,” she says.

The study was funded by the Canadian Institutes of Health Research (CIHR), Heart and Stroke Foundation of Canada, and Pharmacia and UpJohn.

To read the full release, visit thelancet.com