A Prospective Longitudinal Study of Immunoreactive Prostacyclin and Thromboxane Metabolites in Normal and Hypertensive Pregnancy

Abstract

Prostacyclin (PGI₂) and thromboxane (TxA₂) have been implicated in the pathophysiology of PIH. A prospective longitudinal study of maternal plasma levels of PGI₂ and TxA₂ metabolites measured by radioimmunoassay, was carried out in 14 pregnancies. In the eight pregnancies which remained normal, PGI₂ metabolites (PGI₂ M) were significantly increased in the first as compared to the second and third trimesters. Six pregnancies were complicated by mild to moderate PIH in the third trimester. PGI₂ M levels were not significantly different from the normal group in the first and second trimesters, but fell to unrecordable levels (< 5pg/ml) in all hypertensive patients, with the development of PIH, a feature not seen in any of the normal group. In both groups, levels of TxB₂ the stable metabolite of TxA₂, fell significantly in the second and early third trimesters. Late third trimester TxB₂ levels obtained in the hypertensive group only, were significantly higher than earlier in the third trimester. These results support the hypothesis that PGI₂ deficiency is involved in the pathophysiology of PIH.