Credit: Ninan Matthews
Low-molecular-weight heparin (LMWH) does not reduce complications in pregnant women with thrombophilia, according to a study published in The Lancet.
Thrombophilia increases the risk of pregnancy-associated venous thromboembolism (VTE), pregnancy loss, and placenta-mediated pregnancy complications.
For years, physicians have believed that daily antepartum injections of LMWH can reduce these complications, but results of a randomized trial suggest this is not the case.
The LMWH dalteparin provided no positive benefits for mothers or their children. In fact, the study indicated that LMWH could actually cause pregnant women minor harm by increasing the risk of bleeding, increasing the rate of induced labor, and reducing access to anesthesia during childbirth.
“These results mean that many women around the world can save themselves a lot of unnecessary pain during pregnancy,” said study author Marc Rodger, MD, of the Ottawa Hospital Research Institute in Canada.
“While I wish we could have shown that LMWH prevents complications, we actually proved it doesn’t help. However, I’m very glad that we can now spare these women all those unnecessary needles.”
To assess the safety and efficacy of LMWH, Dr Rodger and his colleagues analyzed 289 pregnant women with thrombophilia who were at an increased risk of VTE or had previous placenta-mediated pregnancy complications.
The subjects were randomized to no treatment (n=143) or antepartum prophylactic doses of dalteparin (n=146)—5000 IU once daily up to 20 weeks’ gestation and twice daily thereafter until at least 37 weeks’ gestation.
Some patients crossed over during treatment. So for the on-treatment and safety analyses, there were 143 patients in the dalteparin arm and 141 in the control arm.
Patients met the primary efficacy endpoint if they experienced 1 or more of the following: severe or early onset pre-eclampsia, a small-for-gestational-age infant (birthweight <10th percentile), pregnancy loss, or VTE.
Results showed that dalteparin did not reduce the incidence of this composite outcome in either the intent-to-treat analysis or the on-treatment analysis.
In the intent-to-treat analysis, 17.1% (25/146) of patients in the dalteparin arm met the endpoint, as did 18.9% (27/143) of those in the control arm. In the on-treatment analysis, 19.6% (28/143) of patients in the dalteparin arm met the endpoint, as did 17% (24/141) of those in the control arm.
The safety analysis revealed no significant difference in the incidence of major bleeding between the dalteparin and control arms—2.1% (3/143) and 1.4% (2/141), respectively.
Minor bleeding was more common in the dalteparin arm than the control arm, occurring in 19.6% (28/143) and 9.2% (13/141) of patients, respectively (P=0.01).
Dr Rodger said he hopes these results will prompt physicians to stop prescribing LMWH to pregnant women with thrombophilia and/or previous pregnancy complications when it isn’t warranted.
“These findings allow us to move on, to pursue other potentially effective methods for treating pregnant women with thrombophilia and/or complications from placenta blood clots,” he said.
He and his colleagues noted, however, that patients with one type of thrombophilia—anti-phospholipid antibodies—may benefit from anticoagulant therapy, as it can prevent recurrent pregnancy loss.
Furthermore, some women should take low-dose aspirin while pregnant to help prevent pregnancy complications. And all women with thrombophilia should receive anticoagulant therapy to prevent thrombosis after delivery.
So it seems that some pregnant women might still benefit from taking anticoagulants, but this requires further study.
