Classification of hypertension in pregnancy

In many ways there should be no need to classify hypertensive disorders in clinical practice. The very presence of rising blood pressure should alert the clinician to seek evidence for the development of pre-eclampsia and whe ther there are any emerging abnormalities of fetal growth and/or maternal r enal, cerebral, hepatic or coagulation functions which may necessitate spec ific treatment, including delivery. While such a view may be appropriate fo r experienced clinicians with an understanding of the pathophysiology of th e hypertensive disorders of pregnancy, it is of little help to junior or le ss experienced medical staff. Moreover, without an agreed international cla ssification system it is impossible to compare truly clinical outcome, inte rvention or basic research studies from different units; as entry criteria to these studies may differ considerably across individual units and certai nly across countries. In this chapter we highlight the limitations of the e xisting classification systems and propose a system that is based on our pr esent understanding of the pathophysiology of pre-eclampsia. The proposed s ystem is not a radical departure from previous classifications, with groupi ng of hypertensive subjects into gestational hypertension, pre-eclampsia an d chronic (usually essential) hypertension. Proteinuria, while remaining a hallmark of pre-eclampsia, is no longer considered a 'sine qua non' for thi s disorder to be diagnosed, reflecting our greater understanding of the mat ernal and fetal abnormalities in preeclampsia since previous classification systems were developed. This classification system has been compared with the traditional system of diagnosing proteinuric pre-eclampsia in a study o f 1183 women with hypertension in pregnancy: diagnosing pre-eclampsia in th is new manner still stratifies a high-risk group of pregnant women and the proposed diagnosis of gestational hypertension in this system stratifies a group of women at low maternal and fetal risk, provided that continual mate rnal and fetal monitoring is employed. We hope that this system of classifi cation can be adopted uniformly, permitting appropriate triage of pregnant women into higher and lower clinical risk groups while allowing us to compa re 'apples with apples' in future research studies.