The Safety of Low-Molecular-Weight Heparin Therapy During Labor

Abstract

For some years, low-molecular-weight heparin (LMWH) has been widely used to prevent thromboembolic complications in pregnancies at risk. Its safety has been well established in previous studies. This study was designed to determine the safety of discontinuing LMWH for 12 to 24 hours before vaginal delivery or an invasive procedure. Hemorrhagic and other complications were surveyed in 284 women given enoxaparin during pregnancy and in 16,132 others not given this treatment. Enoxaparin was self-administered by subcutaneous injection, as a preventive measure (0.5–1 mg/kg daily) in 84% of women, and therapeutically (1.5–2 mg/kg daily) in the remaining 16%. Postpartum hemorrhage was defined as an estimated loss of more than 500 mL of blood after vaginal delivery, more than 1000 mL after cesarean section, or a drop of at least 2 gram% of hemoglobin or 10% in hematocrit 24 to 72 hours after giving birth. The duration of treatment averaged 251 days and included at least 6 postpartum weeks. Nearly one fourth of treated women had previously experienced thromboembolism. The treated and untreated women were similar in age and pregestational body mass index. Postpartum hemorrhage was rare in both groups, occurring in 2.1% of treated women and 1.9% of those not treated. Three of 6 hemorrhages in LMWH-treated women were ascribed to uterine atony after prolonged labor with oxytocin. Four of the 6 treated women with postpartum hemorrhage had their last treatment more than 24 hours earlier. In only one case did the dose of enoxaparin exceed 0.5 mg/kg daily. Just over three fourths of treated women had an epidural catheter placed. The last injection of LMWH generally was given 12 to 24 hours before delivery, cesarean section, or catheter placement. No spinal hematomas were diagnosed. Discontinuing LMWH 12 to 24 hours or longer before vaginal or section delivery did not influence the 5-minute Apgar score, umbilical arterial blood pH, or admission to neonatal intensive care. None of the infants born to LMWH-treated mothers had hemorrhagic complications. LMWH in the form of enoxaparin may be safely discontinued 12 hours before labor is induced whether vaginal or operative delivery is carried out. It also appears that epidural anesthesia is safe if 12 or more hours have elapsed since the last dose of enoxaparin.