Introduction

Hypertensive disorders are the most common medical complication of pregnancy, affecting 6–8% of all pregnancies (National High Blood Pressure Working Group, 2000). Approximately 30% of hypertensive disorders in pregnancy are due to chronic hypertension and 70% are due to gestational hypertension–pre-eclampsia. The spectrum of disease ranges from mildly elevated blood pressures with minimal clinical significance to severe hypertension and multi-organ dysfunction.

Severe pre-eclampsia is a clinical syndrome that can progress rapidly to an obstetric emergency. It embraces a spectrum of signs and symptoms, primarily systolic or diastolic blood pressure (BP) exceeding 160 or 110 mmHg, respectively, significant proteinuria (>5 g in a 24 h specimen), and evidence of end-organ damage. In healthy nulliparous women, the rate of severe pre-eclampsia is 2–3% (Sibai et al., 1993). It accounts for a significant proportion of indicated preterm deliveries and contributes to maternal and neonatal morbidity and mortality (Kurkinen-Raty et al., 2000; Mackay et al., 2001; Waterstone et al., 2001). Until recently, women with severe pre-eclampsia were delivered without delay regardless of gestational age. When pre-eclampsia occurred remote from term, this practice usually resulted in a nonviable fetus or an extremely low-birthweight infant. Not until the early 1980s was expectant management considered a legitimate option for severe pre-eclampsia.