Low-Molecular-Weight Heparin May Help Prevent Miscarriage

New Orleans, LAA symposium yesterday heard the latest position on the use of heparin and aspirin—and how the combo does or does not decrease the risk of miscarriage in pregnant women.

Blood clots that form in blood vessels that feed the placenta could rob a developing fetus of life-giving nutrients, and scientists suspect that abnormal blood clots play a role in recurrent miscarriages. The use of low-molecular-weight heparin and aspirin may help prevent the recurrence of miscarriages—however, evidence of this remains elusive, according to a PR Newswire item dated December 6.

To test the effectiveness of these controversial treatments, a team of researchers from the Netherlands conducted a multicenter, randomized clinical trial of 364 women between the ages of 18 and 42 who were less than six weeks pregnant or were attempting to conceive. Each woman had previously experienced at least two unexplained miscarriages by the twentieth week of pregnancy. The researchers focused on miscarriages with unexplained causes, and so excluded from the study women with previous clotting disorders, endocrine disorders, or other indications for anticoagulant treatment during pregnancy.

Three treatment groups were compared: aspirin and nadroparin (a low-molecular-weight heparin), aspirin alone, and placebo. Oral medication was administered once a day through 36 weeks of gestational age or until miscarriage, ectopic pregnancy, or premature delivery. Patients on the oral regimens received either placebo pills or 100 mg of calcium carbasalate (a salt formulation of aspirin equivalent to 80 mg of aspirin). Women who were to receive low-molecular-weight heparin received subcutaneous injections once a day of 2,850 international units of nadroparin from six weeks of gestational age through 12 hours before delivery.

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) as compared with 50.8 percent in the aspirin group (61 women) and 57 percent of the placebo group (69 women).

"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.

Dr. Kaandorp presented his findings yesterday at the 51st annual meeting of the American Society of Hematology in New Orleans.