Prostacyclin production during pregnancy: comparison of production during normal pregnancy and pregnancy complicated by hypertension.

We investigated prostacyclin (PGI2) biosynthesis during pregnancy by measuring urinary excretion of 2,3-dinor-6-keto-prostaglandin F1 alpha (dinor) and 15-keto-13,14-dihydro-2,3-dinor-6-keto-prostaglandin F1 alpha (15 kd dinor) with the use of specific gas chromatography-mass spectrometry assays. Nine normotensive nonpregnant women, five normotensive women in the mid-trimester of pregnancy, eight normotensive women in the third trimester of pregnancy, and six women who developed hypertension during the third trimester provided 24-hour samples of urine. Normal pregnant women had a fivefold increase in urinary excretion of dinor in comparison to nonpregnant women (253 +/- 21 ng dinor/gm creatinine for controls vs. 1,224 +/- 110 and 1,127 +/- 152 for second and third trimesters) (mean +/- SEM). Pregnant subjects with hypertension had a significant (50%) reduction in urinary dinor excretion in comparison to normotensive pregnant subjects (561 +/- 105 ng dinor/gm creatinine). In subjects selected from each group, the ratio of dinor to 15 kd dinor remained constant. We conclude that PGI2 biosynthesis is increased during normal pregnancy, and that this increase is less in pregnancy-induced hypertension. This raises the possibility that PGI2 helps mediate hemodynamic changes during normal pregnancy, and that a relative decrease in production might be related to the pathogenesis of pregnancy-induced hypertension.