Blood transferrin receptor expression in chromosomally abnormal fetuses.

In a cross-sectional study of 13 chromosomally abnormal fetuses, umbilical venous blood was obtained by cordocentesis at 17-32 weeks' gestation. Fetal blood transferrin receptor (CD71) expression (mean = 79.8 per cent, range = 60-98 per cent) and nucleated red cell count (mean = 10.4 x 10(9) per 1, range = 1.0-25.0 x 10(9) per 1) were significantly higher than the appropriate normal mean for gestation (z = 3.92, P < 0.0001 and z = 3.69, P < 0.001, respectively). These haematological changes in chromosomally abnormal fetuses would facilitate their prenatal diagnosis by analysis of fetal nucleated red blood cells isolated from the maternal circulation on the basis of CD71 expression.