Forty-seven fetuses treated with intravenous intrauterine transfusion for rhesus isoimmunization were studied. At the time of first transfusion the fetuses were below average in size with the fetal femur length being directly related to the degree of fetal anemia. Subsequent to transfusion therapy there was increased growth of all fetal parameters measured. Birthweight was similar to a control group of unaffected fetuses. This contrasts with results after intraperitoneal transfusion where birthweights have been reported as being below average.