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Patient Evidence Summary
Doctor, I have an inherited blood clotting disorder and recurrent miscarriages. Will heparin injections prevent miscarriage of my next pregnancy?
Low-molecular weight heparin (LMWH) injections during pregnancy do not reduce the risk of miscarriage or other complications of pregnancy for individuals with inherited blood clotting disorders. Please note these results do not apply to pregnancies in people with Antiphospholipid Antibody Syndrome (APLAS).
Study highlights
For individuals with inherited blood clotting disorders and 2 or more miscarriages, LMWH injections versus no LMWH injections during pregnancy did not differ for number of livebirths or pregnancy losses.
Understanding the problem
When individuals have recurrent miscarriages, they may have their blood tested for inherited blood clotting disorders (e.g., Factor V Leiden mutation, Prothrombin gene mutation, Antithrombin deficiency, Protein C deficiency, Protein S deficiency). It is believed that these clotting disorders may cause tiny blood clots to form in the placenta that can lead to miscarriage. If a clotting disorder is diagnosed, they may be prescribed low-molecular weight heparin (LMWH) injections to give to themselves during their next pregnancy. The hope is that these injections will prevent the tiny blood clots and reduce the risk of miscarriage. However, there has been little research to prove this treatment works.
The researchers in this study wanted to know if LMWH injections started during attempts to conceive or early confirmed pregnancy would reduce the risk of miscarriage and increase the likelihood of individuals diagnosed with inherited blood clotting disorders having a livebirth.
Who? The study included 326 individuals (age 18-42 years) with a history of 2 or more miscarriages or intrauterine fetal death who were attempting to conceive or were less than 7 weeks pregnant and had an inherited blood clotting disorder. Individuals who weighed less than 50 kg or had another reason to use anticoagulants during pregnancy (e.g., prevent DVT or PE in the mother) were excluded.
What? The study compared LMWH injections with no LMWH injections.
LMWH injections | vs | No LMWH injections |
|---|---|---|
enoxaparin 40 mg OR dalteparin 5,000 IU OR tinzaparin 4,500 IU OR nadroparin 3,800 IU injected into the abdomen or leg once a day starting as soon as possible after a positive pregnancy test and before 7 weeks gestation. Injections were continued throughout pregnancy and stopped once labour started. | No injections |
LMWH injections vs no LMWH injections in pregnant individuals with inherited blood clotting disorders
Outcomes | Rate of events with LMWH | Rate of events without LMWH | Results |
|---|---|---|---|
Livebirth | 72 out of 100 people | 71 out of 100 people | No effect* |
Pregnancy loss | 28 out of 100 people | 29 out of 100 people | No effect* |
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could simply be due to chance rather than due to the different treatments.
This Evidence Summary is based on the following article:
Quenby S, Booth K, Hiller L, et al. Heparin for women with recurrent miscarriage and inherited thrombophilia (ALIFE2): an international open-label, randomised controlled trial. Lancet. 2023 Jul 1;402(10395):54-61. doi: 10.1016/S0140-6736(23)00693-1. Epub 2023 Jun 1. PubMed
Lori-Ann Linkins, MD, MSc (Clin Epi), FRCPC
Dr. Linkins is an Associate Professor of Medicine (thrombosis) at McMaster University in Hamilton, Canada. She holds a Masters Degree in Health Research Methodology and is a Deputy Editor with the Health Information Research Unit, McMaster. She is Co-Editor of the ACP Journal Club and Co-lead on the CanVECTOR Knowledge Translation Platform.
Published: Tuesday, October 10, 2023
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from a professional healthcare provider. If you have any questions about any medical matter, you should consult your professional healthcare providers, and should never delay seeking medical advice, disregard medical advice or discontinue medication based on information provided here.
, McMaster University