Low molecular weight heparin for pregnancy complications?

Obstetric and neonatal outcomes in pregnant women treated with high-dose thromboprophylaxis: a retrospective, single-center study

INTRODUCTION

It is well established that women with very high risk of developing antenatal thrombosis benefit from high-dose thromboprophylaxis, however data on outcomes and the safety and efficacy of thromboprophylaxis are scarce. The aim of the study was to evaluate the safety and effectiveness of the Swedish guidelines for high-dose thromboprophylaxis and the obstetric outcomes in a single-center patient cohort.

PATIENTS AND METHODS

Forty-seven women treated at the Department of Obstetrics and Gynecology, Karolinska University Hospital, Solna, Sweden, between 2004 and 2017 were included in this retrospective study. Data on treatment, obstetric, and neonatal outcomes and medical history were collected. Data derived from the Swedish Medical Birth Registry on women giving birth in Stockholm County 2004-2016 were used as controls. The protocol of the study was approved by the Regional Ethics Committee in Stockholm, Sweden.

RESULTS

The initial thromboprophylaxis dose was 5000 IU dalteparin twice daily. No patient developed ablatio placentae or preeclampsia. One patient suffered antenatal muscle vein thrombosis. Six patients (12.7%) suffered postpartum hemorrhage (PPH); however only one patient had severe PPH. Forty-eight children were born. Three children (6%) were diagnosed with intrauterine growth retardation, five (10%) were born small for gestational age and seven (15%) were born premature, the majority of which (except for two premature) to women with thrombophilia.

DISCUSSION

High-dose thromboprophylaxis was effective and safe. The incidence of preeclampsia and ablatio was lower than in controls; however, neonatal outcomes were worse, especially among mothers with thrombophilia. Due to the diversity of the thrombophilic traits, no thrombophilia-specific conclusion could be drawn. Stricter adherence to the guidelines could further decrease the risk for bleeding, whereas more frequent antenatal controls could possible improve neonatal outcomes.

Obstetric complications and pregnancy-related venous thromboembolism: The effect of low-molecular-weight heparin on their prevention in carriers of factor V Leiden or prothrombin G20210A mutation

Whether the administration of low-molecular-weight heparin (LMWH) during pregnancy is effective in preventing obstetric complications and pregnancy-related venous thromboembolism (VTE) in women who are carriers of factor V Leiden (FVL) and/or prothrombin variant G20210A (PTm) is controversial. This observational study investigated the possible efficacy of pharmacological treatment with LMWH ± aspirin (ASA) in pregnancy outcomes in 1,011 pregnancies of 416 women with thrombophilia (FVL and/or PTm). Most patients were chosen on the basis of previous obstetrical complications (36%), or because of familial or personal history of venous/arterial thromboembolism (28% and 18%, respectively); 74 patients (18%) were incidentally identified. The outcome was evaluated according to the type of treatment and of the period of pregnancy when the treatment was started. After adjustment for observation before and after diagnosis of thrombophilia, previous miscarriages and VTE, parity, age and centre, we observed that LMWH had a protective effect on miscarriages (odds ratio [OR] 0.52, 95% confidence interval [CI] 0.29–0.94) and VTE (OR 0.05, 95% CI 0.01–0.21). ASA appeared to have no effect on the prevention of obstetric complications and VTE. A nested analysis performed in 116 women with two or more obstetric complications confirmed that the highest number of live births was recorded in the group under LMWH prophylaxis (OR 0.19, 95% CI 0.05–0.75). These results suggest that LMWH prophylaxis reduces the risk of obstetric complications in carriers of FVL and/or PTm, particularly in those with previous obstetric events. Furthermore, LMWH prophylaxis reduces the risk of pregnancy-related VTE.

Antithrombotic treatment for pregnancy complications: which path for the journey to precision medicine?

Haemostatic and vascular biology mechanisms appear to play an important role in the pathogenesis of placenta-mediated pregnancy complications. Although low-dose aspirin (LDA) has a modest effect in preventing preeclampsia, antithrombotic interventions, LDA and low molecular weight heparin (LMWH) have not definitively proven their effectiveness in women with placenta-mediated pregnancy complications selected by previous pregnancy outcome alone. Given the heterogeneous aetiology of placenta-mediated pregnancy complications, it is critical to stratify patients according to maternal and fetal characteristics and disease mechanisms rather than simply by pregnancy outcome, such as miscarriage. Such stratification could identify those who could benefit from antithrombotic interventions in pregnancy. We lack data on genome-wide association studies, biomarkers and trials of interventions applied to specific homogeneous populations. Future studies should focus on elaborating different disease mechanisms and examining antithrombotic interventions in specific and more homogeneous groups, such as thrombophilic women with well-characterized placenta-mediated pregnancy complications, stratified by disease severity and pathological findings. Because of fetal safety concerns with new anticoagulants, the intervention should focus on heparins alone or in combination with LDA. Thus, placenta-mediated pregnancy complications deserve precision medicine, defining disease by mechanism rather than outcome with interventions focused on a more personalized approach.