Pregnancies complicated by pre-eclampsia, chronic hypertension, or both, are at significantly increased risk of adverse outcomes. For most women, the assessment of blood pressure and urinalysis form the mainstay of routine antenatal care. In the recently published report by the Confidential Enquiry into Maternal and Child Health (CEMACH), pre-eclampsia or eclampsia was the second most common cause of direct maternal mortality in the United Kingdom between 2003 and 2005.1 Although no intervention has been proved to prevent pre-eclampsia, much attention in recent years has focused on improving our ability to predict this common complication.

The accompanying meta-analysis by Cnossen and colleagues examines the relation between early pregnancy blood pressure values and subsequent development of pre-eclampsia.2 In low risk women, mean arterial pressure in the second trimester was a better predictor of pre-eclampsia than systolic blood pressure or diastolic blood pressure. The predictive strength of mean arterial pressure was moderate (area under the receiver operating characteristic curve 0.76), however. The positive and negative likelihood ratios of a second trimester mean arterial pressure of ≥90 mm Hg were 3.5 …