Study of the Efficacy and Safety of AMAG-423 (Digoxin Immune Fab) in Antepartum Subjects With Severe Preeclampsia

Inclusion Criteria: * Fetal gestational age 23 0/7 to 31 6/7 weeks * Treated with expectant management * Meets modified ACOG criteria for severe preeclampsia * Willing and able to provide written, informed consent Exclusion Criteria: * Decision to deliver within 24 hours has been made * Weight \> 150 kg * Eclampsia * Significant antecedent obstetrical problems * Clinically significant fetal anomaly or chromosomal abnormalities * Chronic renal disease * Active hepatic disease, antiphospholipid antibody syndrome, or lupus * Unstable medical or psychiatric disorder * Need for use of digitalis like products * History of anaphylactic allergic reactions * Prior use of antibodies/fab fragments from sheep * Serum creatinine ≥ 2.0 mg/dL * Platelet count \< 50,000 * Pulmonary edema * Estimated fetal weight \< 5th percentile