ObjectiveTo determine whether increased concentrations of the N-terminal peptide of proatrial natriuretic peptide and of atrial natriuretic peptide are related to the severity of preeclampsia and gestational hypertension.MethodsBlood samples were collected from 70 healthy pregnant women, 48 women with preeclampsia, and 19 women with gestational hypertension in the third trimester. We used a specific radioimmunoassay (RIA) method suitable for the determination of the plasma N-terminal peptide of proatrial natriuretic peptide in unextracted plasma. The atrial natriuretic peptide was measured by RIA from Sep-Pak C18-extracted plasma.ResultsThe N-terminal peptide of proatrial natriuretic peptide levels were significantly higher in preeclamptic women than in healthy pregnant controls (median 571 [range 189–20001 versus 266 pmol/L [80-6341,P< .001) and also significantly higher in women with severe preeclampsia than in women with mild preeclampsia (766 [431-20001 versus 492 pmol/L [189–1283],P= .01). The N-terminal peptide of proatrial natriuretic peptide values were significantly elevated in the subgroup of hypertensive pregnancies with abnormal Doppler velocimetry. At entry into the study the values for the N-terminal peptide of proatrial natriuretic peptide were higher in the subgroup of women who developed severe preeclampsia and/or gave birth to a small for gestational age (SGA) infant compared to the values in the subgroup of women in whom the hypertensive condition remained stable (710 [271–1475] versus 407 pmol/L [189–1067],P= .006). Similar comparisons of atrial natriuretic peptide values did not reach significant differences.ConclusionThe levels of N-terminal peptide of proatrial natriuretic peptide were higher in women with preeclampsia than in those with gestational hypertension and higher in women with gestational hypertension than in those with normal pregnancies. A marked elevation in N-terminal peptide of proatrial natriuretic peptide may predict development of severe preeclampsia and/or an SGA infant.