Sildenafil Citrate for the Treatment of Established Pre-Eclampsia

Inclusion Criteria: * Subjects with pre-eclampsia defined as new hypertension with a diastolic BP of \> or = 90 mmHg on two occasions separated by at least 4 hrs arising after 20 weeks of pregnancy, associated with \>500 mg/24 hr proteinuria. Subjects with pre-existing hypertension (on treatment) need only fulfill proteinuria requirement. * Gestational age 24-34 w * Singleton pregnancy Exclusion Criteria: * Where urgent delivery is indicated * Where the fetus is suspected to have a structural or chromosomal abnormality