Giving daily heparin injections to pregnant women with thrombophilia and history of a previous miscarriage fails to lower their risk of such complications, a major international study has shown.
UK experts said the findings were important in reinforcing there is no evidence women with thrombophilia should be given the injections just because they have had a previous miscarriage – but stressed those women who have a history of previous venous thrombosis should still receive heparin during pregnancy.
The open-label randomised trial, published today in The Lancet, was conducted in 36 hospitals across five countries and included 292 pregnant women with thrombophilia who had a history of venous thromboembolism (VTE) or previous placenta-mediated pregnancy complications.
Half the women were assigned to have daily injections of the low-molecular weight heparin dalteparin until 37 weeks’ gestation, while the other half were given no dalteparin.
Researchers found the women who had daily dalteparin injections were no less likely to have the composite outcome of severe or early onset pre-eclampsia, small-for-gestational age infant, pregnancy loss or venous thromboembolism than those women who did not have the injections, with respective rates of 17% and 18% in each group.
However, women who received dalteparin were significantly more likely to experience minor bleeding events, at a rate of 20% compared with 9% in the no-dalteparin group.
Co-author Dr Marc Rodger, senior scientist at Ottowa Hospital in Ontario, Canada, said: ‘These results mean that many women around the world can save themselves a lot of unnecessary pain during pregnancy. Using low molecular weight heparin unnecessarily medicalises a women’s pregnancy and is costly.’
Professor Catherine Nelson-Piercy, obstetric physician at Guys and St Thomas’s Hospital London and lead developer for the Royal College of Obstetricians and Gynaecology guidelines on thromboprophylaxis in pregnancy, told Pulse the findings were ‘very important’ in showing there was no evidence for heparin in women with thromobophilia who have had previous pregnancy complications.
Professor Nelson-Piercy said: ‘At present a lot of obstetricians treat women with thrombophilia who have had previous pregnancy complications without any evidence that it works. It’s very important the results are used to persuade them there is no evidence to support the use of low-molecular weight heparin for this indication.’
However, Professor Nelson-Piercy said that the trial would not change current recommendations to use heparin in women with thrombophilia with a history of VTE as very few participants with such a history were included in the trial, and it only considered a composite outcome.
Professor Nelson-Piercy said: ‘The RCOG guideline is clear that if a woman with thrombophilia has had a previous blood clot she should definitely be recommended to take heparin during pregnancy.The results of this study should not alter that.’