OBJECTIVE: To 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. METHODS: Blood 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. RESULTS: The N-terminal peptide of proatrial natriuretic peptide levels were significantly higher in preeclamptic women than in healthy pregnant controls (median 571 [range 189-2000] versus 266 pmol/L [80-634], P