Since the 1990s, well-meaning physicians have prescribed pregnant patients low-molecular weight heparin to combat complications, especially when thrombophilia or previous complications pose a risk to the mother and child. However, research suggests that there are no benefits and greater risks of increased minor bleeding when taking anticoagulant agents.

Published online July 25 in The Lancet, the international Thrombophilia in Pregnancy Prophylaxis Study (TIPPS) followed 289 pregnant women separated into two groups: those being given prophylactic dalteparin (146) and those who weren’t (143). Patients were enrolled between late February 2000 and mid-September 2012. The intent was that by taking dalteparin, complication risks would be reduced for mothers at risk for blood clots.

The research team, led by Marc Rodger, MD, of the University of Ottawa in Ontario, found that dalteparin use made little difference in outcomes compared with the control group. The intention-to-treat analysis and the on-treatment analysis were similar, favoring no dalteparin in the former and dalteparin in the later, but only by a small margin, since these percentages represented only a few patients in either direction. Instead, minor bleeding was increased in those taking anticoagulants by about 10 percent.

Thromboembolism rates did not increase by withholding the drug during pregnancy, a significant finding as well, when considering that treatment is meant to be as much for the mother as for maintaining pregnancy.

"These results mean that many women around the world can save themselves a lot of unnecessary pain during pregnancy," said Rodger in a press release "Using low molecular weight heparin unnecessarily medicalizes a woman's pregnancy and is costly."

Injections of antepartum anticoagulants can cost upwards of $8,000 over the course of a pregnancy and requires expectant mothers to inject themselves up to 400 times by the end of their pregnancy. If a course of anticoagulants hasn’t been stopped in the 48 hours leading to delivery, access to pain medication is heavily restricted.

Rodger et al found as their research progressed that studies that promoted the benefit of dalteparin in antepartum patients were based on low quality evidence. According to the research team, in order for dalteparin to have significant effect on outcomes, the need-to-treat would be 16 percent, in this case, six patients, which this study did not achieve.

An editorial comment written by Paul S. Gibson, MD, of the University of Calgary and colleagues noted, “This situation draws attention to the fact that clinicians’ altruistic intentions to treat these high-risk women might have inadvertently caused them minor harm, potentially increased the rates of labour induction, reduced access to regional anaesthetics, increased health-care costs (because of the high cost of low-molecular-weight heparin), and slowed the research momentum in this area.”

"These findings allow us to move on, to pursue other, potentially effective, methods for treating pregnant women with thrombophilia and/or complications from placenta blood clots," said Rodger.