Estimating human fetal blood volume on the basis of gestational age and fetal abdominal circumference

Intravascular transfusion of the human fetus is now a standard procedure for the management of fetal anaemia both due to allo-immunisation and parvovirus infection. The volume of blood required to correct a given degree of anaemia depends on the fetal blood volume as well as the severity of the anaemia. While the latter can be measured directly at the time of cordocentesis, the fetal blood volume is estimated on the basis of an empirically derived equation using the relationship between the volume of blood per kilogram of weight at each week of gestation and assuming that the fetus is on the 50th percentile of weight for the given gestational age. In the present study, we sought to test the hypothesis that combining gestational age with an ultrasonic estimate of fetal weight might improve the ability to predict fetal blood volume and thus the posttransfusion haematocrit (Hct).