Endothelin 1-21 plasma levels in fetuses at 18-24 weeks of gestation

This study aimed to establish normal endothelin (ET) ranges in non malformed appropriate for gestational age fetuses of 18-24 weeks gestation and to investigate a possible correlation between maternal and fetal ET plasma levels. Twenty "mother-fetus" pairs were included in the study. The determination of ET 1-21 was performed by radioimmunoassay using 1 ml of fetal blood obtained by cordocentesis--indicated for various reasons--and in 2 ml of maternal venous blood. The statistical analysis involved the Wilcoxon test for pair differences and the Spearman rank correlation coefficient. Fetal and maternal ET 1-21 levels were respectively 11.39 +/- 2.22 pmol/L and 6.44 +/- 1.00 pmol/L. Fetal levels were significantly higher (p < 0.01) thus excluding passive ET transfer through the placenta, while no correlation between maternal and fetal levels was found. It is speculated that high fetal ET 1-21 levels result from increased ET production, which possess cell proliferative properties and/or decreased ET removal from the fetal circulation because of hypofunctioning lungs and kidneys. It can be assumed that the increased amounts of fetal ETs contribute to normal growth and development directly as well as by regulating vascular tonus and local blood flow.