A longitudinal study of plasma renin activity during normal and preeclamptic pregnancy.

In 68 pregnant women, blood samples were obtained at 12, 20, 25, 29, 32 and 36 weeks. Plasma renin activity (PRA) was measured in 10 of them, who developed "pregnancy induced hypertension" ("PIH") and in 10 normal pregnant women, matched with the hypertensive patients for age, parity and body weight. Towards the end of pregnancy, PRA showed a tendency to increase in the "PIH" group, and to decrease in the control group. However, these variations were not statistically significant. There was no significant difference between the two groups, except for the last measurement, obtained at the 36th week of gestation. At this time, PRA was more elevated in the PIH group. We conclude that PRA measurements early in pregnancy are of no value in predicting if women are going to develop PIH.