Fetal circulatory endothelin-1,2 in the midtrimester.

Umbilical-vein blood from eight fetuses who underwent cordocentesis for rapid karyotyping at 19-22 gestational weeks was tested for immunoreactive endothelin-1,2 by means of radioimmunoassay. Endothelin was detected in the serum of all but one of these fetuses. Levels of endothelin-1,2 ranged from 8.5 to 19.2 fmol/ml (mean 13.4 fmol/ml). We speculate that endothelin in the fetoplacental circulation may play a role in the regulation of fetal hemodynamics in utero.