The assessment of endothelial function in pregnancy by flow-mediated dilatation.

Abstract

The endothelium plays a major role in the regulation of vascular homeostasis in pregnancy. Endothelial dysfunction has been implicated in the pathophysiology of many diseases, including hypertension and pre-eclampsia. The aim of this work was to assess endothelial function in pregnancy. The ultrasound technique used was flow-mediated dilatation, a marker of stimulated endothelial function. The technique involves inducing reactive hyperaemia with a blood pressure cuff. Brachial artery diameter is measured pre and post cuff release and flow-mediated dilatation is the percentage increase in artery diameter. First, a longitudinal study to develop a normal range of endothelial function in pregnancy and postpartum was performed and compared with non-pregnant women. The study demonstrated endothelial function did not vary throughout pregnancy until 36+ weeks gestation after which it decreased significantly. This decrease is in accordance with the normal physiology of pregnancy. No significant difference in endothelial function was demonstrated between non-pregnant women and pregnant/post-partum women. Second, a study assessing the effect of smoking on the endothelium in pregnancy was completed. Smoking in pregnancy was found to induce endothelial dysfunction. When women smoked and had growth restricted babies their endothelial function was significantly decreased compared to women with normally grown fetuses. The final study tested endothelial function in women who developed pre-eclampsia and gestational hypertension. Women with gestational hypertension had endothelial dysfunction. Endothelial function in the pre-eclamptic women was similar to the normal range result. The women in this study were in the obese range and most had late pre-eclampsia. These results reinforce the message that pre-eclampsia may not be a homogeneous disorder. In conclusion, endothelial function can be assessed non-invasively in pregnancy. Women with gestational hypertension and pre-eclampsia demonstrate differences in endothelial function. Smoking in pregnancy results in endothelial dysfunction. This work provides a basis for future research on endothelial function in pregnancy, especially the hypertensive disorders of pregnancy.