Natriuretic peptide levels in intrauterine growth-restricted fetuses with absent and reversed end-diastolic flow of the umbilical artery in relation to ductus venosus flow velocities.

Objective: To determine if changes in natriuretic peptide levels [propeptide of atrial natriuretic peptide (proANP) and N-terminal propeptide of brain natriuretic peptide (NT-proBNP)] can be demonstrated in fetuses with serious growth restriction and Doppler ultrasonographic findings of hemodynamic compromise. Method: Natriuretic peptides of the umbilical vein (proANP and NT-proBNP), arterial and venous blood gases, as well as lactate levels of the umbilical vein were determined in 38 appropriate for gestational age (AGA) fetuses, and 24 intrauterine growth-restricted (IUGR) fetuses with absent (zero-flow) and 17 IUGR fetuses with reversed end-diastolic flow (reverse-flow) of the umbilical artery. Results: A continuous increase in natriuretic peptides in the presence of progressive deterioration was shown. ANP concentrations were significantly lower in the AGA group (mean 818 fmol/mL; range 508-991 fmol/mL) than the zero-flow group (mean 19,680 fmol/mL; range 13,680-25,080 fmol/mL) and the reverse-flow group (mean 33,880 fmol/mL; range 24,365-41,786 fmol/mL). Significant differences were further demonstrated in BNP concentrations of the AGA group (mean 32 fmol/L; range 25-38 fmol/L), zero-flow group (mean 1191 fmol/L; range 908-1655 fmol/L), and reverse-flow group (mean 3063 fmol/L; range 1281-4968 fmol/L). Additionally, significant differences in lactate concentrations were observed for the three groups: AGA, 2.6 mmol/L (range 2-3 mmol/L); zero-flow group, 4.1 mmol/L (range 3.3-5 mmol/L); and reverse-flow group, 7.7 mmol/L (range 5.9-13.7 mmol/L). Increased ANP levels correlated with the arterial base excess and lactate concentrations, as well as with the flow velocities in the ductus venosus during atrial contraction (a-wave), and both ductus venosus indices (S-a)/D and (S-a)/V-mean. No correlations were established for BNP. Conclusions: As components of a compensatory mechanism, natriuretic peptides exert an influence on the cardiovascular function of the fetus.