The common practice of giving daily low molecular weight heparin (LMWH) to women to prevent recurrent pregnancy loss (RPL) may not be an effective intervention, according to a new study. In a randomized, controlled trial from Germany and Austria, some 450 women with at least two consecutive early miscarriages or one late miscarriage were randomized to dalteparin (Fragmin) injections for up to 24 weeks’ gestation, while the control group received only prenatal vitamins. At 24 weeks, there was no difference in the percentage of pregnancies between the two groups (86.8% LMWH group vs 87.9% control group), and the live birth rates were also similar (86.0% LMWH vs 86.7% control, absolute difference -0.7 percentage points; 95% confidence interval, -7.3 to 5.9 percentage points). The rates of pregnancy complications were similar in the two groups. The authors conclude that LMWH injections “do not increase ongoing pregnancy or live-birth rates in women with RPL. Given the burden of injections, they are not recommended for preventing miscarriages.” (Ann Intern Med 2015;162:601-609; doi:10.7326/M14-2062). An accompanying editorial suggests that the future of LMWH in RPL is not clear. It should not be prescribed before 12 weeks’ gestation based on this current study, but “we should seek to understand the pathophysiologic molecular backbone of this syndrome. This may enable relevant and targeted therapeutic interventions.” (Ann Intern Med 2015;162:658-659; doi:10.7326/M15-0564).