Secretion of atrial natriuretic peptide and digoxin-like immunoreactive substance during pregnancy

We investigated the secretion of atrial natriuretic peptide (ANP) and digoxin-like immunoreactive substance (DLIS) during pregnancy, labor, and the puerperium, as measured in maternal and umbilical cord plasma. There were no significant changes in maternal concentrations of ANP during all three periods, and the concentrations were similar to those found in nonpregnant controls and in umbilical cord plasma. Maternal concentrations of DLIS increased significantly in the second half of pregnancy, peaked during labor, then decreased abruptly within 24 h of expulsion of the infant and placenta to values approaching the nonpregnant range. DLIS concentrations in umbilical cord plasma, however, were significantly higher than in maternal plasma during labor. The abrupt fall in DLIS in maternal plasma and the absence of a significant difference in DLIS concentrations between arterial and venous cord plasma suggest that, during pregnancy, the fetus, not the placenta, is the source of DLIS in maternal plasma.