Umbilical artery reactivity and ultrastructural changes in pregnancy‐induced hypertension and other complicated pregnancies

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Abstract
Summary. Abnormal pressor responses are known to occur in the maternal circulation in pregnancy‐induced hypertension (PIH), but little is know of the response of the foetal circulation. The responsiveness of umbilical arteries in PIH can be studied after delivery, and this is a useful model to explore the pathophysiological mechanisms involved.In the present experiments, the in vitro response of umbilical artery rings to bradykinin and 5‐hydroxytryptamine (5‐HT) was tested and ultrastructural changes investigated. Umbilical arteries from 48 cords were studied. Fifteen of the mothers had PIH, five had essential hypertension pre‐dating the pregnancy and five had diabetes. Twenty‐three women had pregnancies uncomplicated by hypertension or serious medical or obstetric problems and these served as controls. Umbilical arteries from the severe proteinuric PIH group were significantly more responsive to 5‐HT as assessed by affinity constants (P <0·05). The responsiveness of arteries from all other groups did not differ from the normal cases. A probable mechanism for the findings is endothelial damage as a result of pre‐eclamptic disease. This was substantiated by ultrastructural evidence.