The advent of cordocentesis has made it possible to treat fetuses affected by severe red cell alloimmunization by infusing red cells into umbilical vessels. In addition, serial hematocrits can be followed between transfusions. Twenty fetuses underwent a total of 118 intrauterine procedures. Four transfusion techniques were compared to assess the effect of each method on the stability of the fetal hematocrit between procedures. The change in hematocrit per day for direct intravascular transfusion was -1.06 ± 0.68%, for intraperitoneal transfusion: +0.03 ± 0.6%, for combined exchange intravascular and intraperitoneal transfusion: +0.02 ± 0.3% and for combined direct intravascular and intraperitoneal technique: -0.01 ± 0.4%. The greatest fall in hematocrit was noted with the use of the direct intravascular technique alone (p < 0.001). The combined direct intravascular/intraperitoneal approach produces a stable hematocrit between procedures and offers the possibility of performing intrauterine transfusions at less frequent intervals.