Circadian rhythm of ANP, Aldosterone and PRA in normotensive IUGR

OBJECTIVE : Atrial natriuretic peptide (ANP) increases are reported during normal pregnancy, but the relation to arterial pressure and the renin-angiotensin system is debatable. We assessed whether normotensive pregnancies with intrauterine growth retardation (IUGR) present an alteration of maternal ANP levels. DESIGN : A total of 11 pregnant women with IUGR, in the absence of any other maternal or fetal pathology, entered the study during the third trimester. They were compared with 12 healthy pregnant women of similar age and characteristics. We monitored all subjects for blood pressure (BP), ANP, aldosterone and plasma renin activity (PRA), under the same conditions for 24 h. All subjects were submitted to the same regimen of life; with homogeneous dark : light periods, salt intake and meal times. METHODS : BP was monitored at 20 min intervals for 24 h and blood tests performed at six time points during the 24 h. EDTA plasma samples were immediately centrifuged. Hormone assays were performed by radioimmunoassay. Koch's nonparametric two-way analysis of variance (ANOVA) was used to compare the hormone time-dependent profiles in the two groups. Circadian rhythms were assessed by cosinor analysis. RESULTS : The IUGR group was characterized by higher ANP values compared to normal pregnancy, (205 +/- 24 versus 146 +/- 21 pg/ml: P < 0.05) but not significant differences were shown for PRA, aldosterone and BP circadian rhythms. CONCLUSIONS : This study shows higher ANP values in human pregnancy complicated by IUGR, with presence of normal BP, aldosterone and PRA profiles.