Aspirin to prevent miscarriage ineffective

Research presented at the 51st Annual Meeting of the American Society of Hematology reveals that the practice of using the anticoagulants aspirin and heparin with the hope of preventing clots in placental blood vessels is ineffective for preventing unexplained, recurrent miscarriages.

Recurrent miscarriages are extremely traumatic and stressful for women, and, according to the American Society for Reproductive Medicine, the cause is unknown in more than 50 percent of cases. Though treatments to avoid these tragedies remain elusive, some practitioners suspect that abnormal clots in the blood vessels that nourish the placenta are responsible for many recurrent miscarriages, and thus they have increasingly used aspirin and low-molecular-weight heparin to prevent further miscarriages, even though evidence to support their use is not available.

A randomized clinical trial of 364 women between the ages of 18 and 42 who were attempting to conceive or were less than six weeks pregnant. The women had previously experienced at least two unexplained miscarriages by the 20th week of pregnancy.

During the study, three treatment groups were compared: aspirin and nadroparin (a low-molecular-weight heparin), aspirin alone, and placebo. The intention-to-treat analysis of the study showed that the live birth rate did not differ significantly among the three treatment groups: 54.5 percent of those in the aspirin and nadroparin group had a live birth (67 women), compared with 50.8 percent in the aspirin group (61 women), and 57 percent of the placebo group (69 women). Side effects, most notably skin reactions, also occurred more often in women assigned to the aspirin and nadroparin group.

"The study clearly demonstrates that aspirin combined with heparin and aspirin alone do not prevent recurrent, unexplained miscarriages and that we should not needlessly put these women through the inconvenience and risks associated with these blood-thinning medications," said lead study author Stef P. Kaandorp, MD, research fellow in the Department of Obstetrics and Gynecology at the Academic Medical Center in Amsterdam. "These results are extremely important because they will likely change the way some women at high risk for another miscarriage have been treated."