The uteroplacental circulation in hypertensive disorders of pregnancy; Doppler ultrasound and histopathological studies

GENERAL INTRODUCTION In the past fifty years, mother and child care in many parts of the world has developed to a high standard, and maternal and perinatal mortality figures have declined dramatically. As complications of illegal abortions, infections and death from postpartum haemorrhage are rarely seen these days in developed countries, hypertensive disorders of pregnancy and their complications now rank as the major cause of maternal mortality in this part of the world. In addition, hypertensive disorders of pregnancy are strongly associated with fetal growth restriction and prematurity, contributing largely to perinatal morbidity and mortality. Over the past decades, our understanding of this unique clinical syndrome has changed dramatically. In the past, hypertension was seen as the hallmark of the clinical picture. All other clinical features were considered as merely secondary to increased arterial pressure. Today, our view of hypertensive disorders of pregnancy is of a systemic disease characterised by widespread endothelial damage which originates from the uteroplacental circulation but ultimately involves a variety of other organs such as the kidney, liver and brain. Despite the progress made in the past decades, the pathophysiology remains largely elusive. Maladaptation of the vasculature of the uteroplacental unit due to impaired trophoblast invasion has often been implicated as the main causal factor, and this view is now widely accepted. Based on this theory, it should be possible to predict which pregnancies are at risk of developing hypertensive disorders of pregnancy by using Doppler ultrasonography to analyse the uteroplacental circulation in the second trimester. However, Doppler screening studies which have been conducted in the past with this objective show variable and often disappointing results. In recent years, a new theory has emerged regarding the etiology of hypertensive disorders of pregnancy. Maladaptation of the uteroplacental vasculature is still seen as an important factor, but it may not play a role in all cases of hypertensive disorders of pregnancy. Especially milder forms, in which the onset of symptoms is at or near term, could be the result of underlying (latent) maternal disorders such as essential hypertension, renal disease or diabetes mellitus which render the uteroplacental vasculature vulnerable to accelerated atherosclerosis or increased vascular tone