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

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.