Maternal complications and pregnancy outcome in women with mechanical prosthetic heart valves treated with enoxaparin

BJOG. 2009 Nov;116(12):1585-92. doi: 10.1111/j.1471-0528.2009.02299.x. Epub 2009 Aug 14.


Objective: To determine maternal and fetal outcomes in women with mechanical heart valves managed with therapeutic dose enoxaparin during pregnancy.

Design: Retrospective audit.

Setting: Hospital-based high-risk antenatal clinics.

Population: Pregnant women with mechanical heart valves attending high-risk antenatal clinics, treated with enoxaparin (1 mg/kg twice daily) during pregnancy.

Methods: Women with mechanical heart valves treated with enoxaparin at any stage during pregnancy (1997-2008) identified using a database of women with mechanical heart valves attending the high-risk clinics and a prospective database of women prescribed enoxaparin for any indication during pregnancy.

Main outcome measures: Maternal outcomes included thromboembolic and haemorrhagic complications. Pregnancy and fetal outcomes included miscarriage, stillbirth, baby death and live birth, small-for-gestational-age infants, warfarin embryopathy and warfarin-related fetal loss.

Results: Thirty-one women underwent 47 pregnancies. In 34 pregnancies (72.3%), anticoagulation was with predominantly enoxaparin and 13 (27.7%) pregnancies women received mainly warfarin, with enoxaparin given in the first trimester and/or peri-delivery. Seven (14.9%) thrombotic complications occurred, of which five (10.6%) were associated with enoxaparin treatment. Non-compliance or sub-therapeutic anti-Xa levels contributed in each case. Antenatal and postpartum haemorrhagic complications occurred in eight (17%) and 15 (32%) pregnancies respectively. Of 35 pregnancies continuing after 20 weeks' gestation, 96% (22/23) of women taking predominantly enoxaparin had a surviving infant compared with 75% (9/12) in women taking primarily warfarin. Four perinatal deaths occurred, three attributable to warfarin.

Conclusions: Compliance with therapeutic dose enoxaparin and aspirin during pregnancy in women with mechanical heart valves is associated with a low risk of valve thrombosis and good fetal outcomes, but close monitoring is essential.

Publication types

  • Multicenter Study

MeSH terms

  • Anticoagulants / administration & dosage
  • Anticoagulants / adverse effects*
  • Delivery, Obstetric / methods
  • Drug Administration Schedule
  • Drug Monitoring / methods
  • Enoxaparin / administration & dosage
  • Enoxaparin / adverse effects*
  • Female
  • Heart Valve Prosthesis / adverse effects*
  • Humans
  • Infant, Newborn
  • Maternal-Fetal Exchange
  • Patient Compliance
  • Pregnancy
  • Pregnancy Complications, Cardiovascular / etiology*
  • Pregnancy Complications, Cardiovascular / prevention & control
  • Pregnancy Outcome
  • Prenatal Exposure Delayed Effects
  • Retrospective Studies
  • Thromboembolism / etiology*
  • Thromboembolism / prevention & control
  • Uterine Hemorrhage / chemically induced
  • Warfarin / adverse effects
  • Warfarin / therapeutic use


  • Anticoagulants
  • Enoxaparin
  • Warfarin