Heparin does not prevent miscarriage for women with inherited thrombophilia, study shows

Based on this new evidence, our researchers are now advising doctors to stop offering the anticoagulant Low Molecular Weight Heparin (heparin) to people with inherited thrombophilia – a condition where the blood has an increased tendency to form clots in veins and arteries. 

Research continues to recommend heparin for those with acquired thrombophilia, however, as evidence shows it can reduce miscarriage risk. Heparin, aspirin, or a combination of the two, continues to be recommended for antiphospholipid syndrome, an immune system disorder and most common form of acquired thrombophilia, which can cause pregnancy complications including recurrent miscarriage. 

Despite the lack of evidence and guidance, doctors often prescribe heparin to women with recurrent miscarriage and inherited thrombophilia. But it’s costly for health services, and inconvenient for women and birthing people who must inject the drug daily and are more likely to experience bruising as a result. 

Stopping screening for inherited thrombophilia and ending the use of heparin as a treatment for it could save the NHS around £20m per year, our researchers say, with funding diverted to other miscarriage services or treatments. 

A new study funded by the National Institute for Health and Care Research (NIHR) and published in The Lancet on Wednesday 31 May shows that a daily injection of heparin does not improve the chance of a live birth for women who have previously had 2 or more miscarriages and confirmed inherited thrombophilia, when compared to standard care. 

Led by Professor Siobhan Quenby, Deputy Director of the Tommy’s National Centre for Miscarriage Research and Professor of Obstetrics at the University of Warwick, the ALIFE2 trial recruited women from 40 hospitals in the UK, Netherlands, USA, Belgium and Slovenia. 

326 women with inherited thrombophilia and recurrent miscarriage were split into 2 groups – 164 received heparin across the course of their pregnancy, starting from as soon as possible after a positive pregnancy test and ending at the start of labour. 162 were not offered the medication.  

All women received standard obstetrician-led care and all women were encouraged to take folic acid. 

The rate of live births for each group was roughly the same:

116 women (71.6%) treated with heparin had a baby born alive after 24 weeks’ pregnancy.

112 women (70.9%) in the standard care group had a baby born alive after 24 weeks’ pregnancy. 

The risk of other pregnancy complications, such as miscarriage, babies with low birth weight, placental abruption, premature birth or pre-eclampsia, was about the same for both groups.  

As expected, bruising easily was reported by 73 (45%) of women in the group taking heparin (mostly around injection-sites) and only 16 (10%) in the standard care group. 

Professor Quenby says:

“Based on these findings, we don’t recommend the use of Low Molecular Weight Heparin for women with recurrent pregnancy loss and confirmed inherited thrombophilia.  

“We also suggest that screening for inherited thrombophilia in women with recurrent pregnancy loss is not needed. Patients and doctors will always value knowing about any factor which could be associated with recurrent miscarriage, but the association between inherited thrombophilia and recurrent miscarriage isn’t proven: a recent review of research showed that thrombophilia is as common in the general population as it is in women with recurrent miscarriage. 

“Many women with recurrent miscarriage around the world are tested for inherited thrombophilia and are treated with heparin daily. Research now shows that this screening is not needed, the treatment isn’t effective, and it is giving false hope to many by continuing to offer it as a potential preventive treatment.” 

28% of women who participated in the trial lost their badly wanted pregnancies, and these unexplained losses will be the focus of further study, as our researchers continue to search for answers and treatment to prevent early pregnancy loss.