Heparin may not reduce miscarriage rates in women with recurrent pregnancy loss

1. In this multicenter trial, low-molecular-weight heparin (LMWH) did not outperform a multivitamin control for prevention of miscarriage in women with unexplained recurrent pregnancy loss.

2. LMWH also did not improve the live birth rate in these women.

Evidence Rating Level: 2 (Good)

Study Rundown: Unexplained recurrent pregnancy loss (RPL) is an emotionally traumatizing condition that affects around 5% of women worldwide. Previously, multiple randomized studies produced conflicting results regarding the efficacy of LMWH for preventing miscarriages in women with RPL. In this current study, women with a history of RPL were randomized into two groups: one group received a multivitamin containing folic acid, while the other group received the same multivitamin plus daily injections of LMWH. LMWH use in the treatment group was stopped at 24 weeks’ gestation. The primary outcome was ongoing pregnancy rate at 24 weeks’ gestation, with a secondary outcome of live birth rate. For both, there was no significant difference between the two groups of women. This study was limited in that it was blinded for neither the patients nor the clinical staff who participated in the trial. Additionally, the control group did not receive placebo injections to mimic the LMWH injections received by the treatment group. However, this study’s findings suggest that LMWH may not be effective for the treatment of unexplained RPL.

Click to read the study published today in the Annals of Internal Medicine

Relevant Reading: Antithrombotic therapy for pregnancy loss

In-Depth [randomized controlled trial]: This multicenter trial conducted in Germany and Austria randomized 434 women with a history of RPL who were between 5 and 8 weeks’ gestation to receive either a multivitamin or multivitamin plus daily LMWH injections. RPL was defined as either 2 or more early-term miscarriages or 1 or more late-term miscarriages. Randomization was stratified based on week of gestation, trial site, and inherited thrombophilia using a minimization protocol. At 24 weeks’ gestation, 86.8% of women in the treatment group had intact pregnancies and 87.9% of women in the control group had intact pregnancies (AD, -1.1 percentage points; p=0.75). The live birth rates were nearly identical at 86.0% in the treatment group and 86.7% in the control group (AD, -0.7 percentage points; p=0.84). Differences were found in the rates of additional secondary outcomes, such as preeclampsia and intrauterine growth restriction, but these were not statistically significant.

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