When to perform the next intra-uterine transfusion in patients with Rh allo-immunization: combined intravascular and intraperitoneal transfusion allows longer intervals.

Data from 99 intra-uterine transfusions performed in 30 patients (31 fetuses) with Rh allo-immunization have been reviewed. Mean gestational age at the first transfusion was 23.6 weeks and mean fetal haematocrit 19.8%. The number of procedures was on average 3.2 per fetus. Survival rate was 84%. Fifty-nine intravascular transfusions were combined with intraperitoneal transfusions. Combined intravascular and intraperitoneal transfusions, when compared to intravascular transfusions alone, achieved a significantly longer interval between transfusions and also maintained a higher fetal haematocrit at the subsequent transfusion. Mean fall in fetal haematocrit was 0.98% per day with a wide range. There was a general tendency towards a less marked fall during the second interval between transfusions than in the first with the exception of those cases in which the percentage of fetal red cells at the start of the second transfusion was increased compared to that which was found at the end of the first, i.e., when fetal erythropoiesis was not suppressed.