Determinants of fetal and maternal atrial natriuretic peptide concentrations at delivery in man.

Matched maternal venous (MV), umbilical artery (UA) and umbilical vein (UV) concentrations of atrial natriuretic peptide [ANP] were measured in 36 normotensive women at term delivery (23 vaginal, 13 caesarean) and 17 non-pregnant women in the first half of the menstrual cycle. MV [ANP] at caesarean section was similar to that in non-pregnant women, but UA and UV [ANP] were higher (P less than 0.01 for both). UA, but not UV, [ANP] was markedly raised after vaginal delivery. Plasma concentrations of aldosterone [ALD] were measured in 16 of the matched sets of samples. No statistically significant association was found between [ANP] and [ALD] in either maternal or fetal samples. Neither maternal nor fetal [ANP] correlated with serum Na+ or osmolality, haematocrit, blood pressure or heart rate.