Renal Function in Gravidas with Chronic Hypertension with and Without Superimposed Preeclampsia

Objective: To assess the predictive value of different renal laboratory tests for development of superimposed preeclampsia in women with chronic hypertension.Methods: Thirty-seven pregnant patients with chronic hypertension and 14 healthy pregnant women were examined at 11-13,19-21, 27-29, and 31-33 weeks with the following laboratory tests: plasma concentrations of creatinine, urea and uric acid, urinary excretion of albumin, and calcium; erythrocyte excretion was investigated only at 11-13 and 27-29 weeks.Results: Among the patients who developed superimposed preeclampsia (30%), a pathologic urinary albumin excretion, i.e., microalbuminuria, was seen in 30% at 31-33 weeks pregnancy, as compared to none among patients with chronic hypertension who did not develop this complication and 7% in the normotensive women (P < 0.05, chi-square test). There was no difference between the groups at the earlier gestational ages. Plasma urea concentration tended to be lower among the normotensive women than in the other two groups only at 19-21 and 27-29 weeks (P < 0.05, P = 0.065, respectively, oneway ANOVA). Plasma urea levels tended to increase with gestational length in those with superimposed preeclampsia, whereas it decreased in the other two groups (P<0.05, ANOVA with repeated measures). The other laboratory parameters differed in no way between the three groups.Conclusion: Blood and urine sampling every 4 to 8 weeks for assessment of renal function in pregnant women with chronic hypertension seems to be of limited value for the prediction of superimposed preeclampsia.