Late hyporegenerative anemia in neonates with rhesus hemolytic disease.

This study was conducted to determine the risk factors of the late hyporegenerative anemia in Rh-isoimmunized infants. Data on 36 infants with rhesus hemolytic disease were analyzed. The mean gestational age and birth weight were 36 +/- 1.3 weeks and 2837 +/- 403 grams respectively. Twenty-seven infants (75%) received between 2 and 8 intravascular intrauterine blood transfusions. Fourteen infants (39%) required simple packed red blood cell transfusions and 11 infants (31%) required exchange blood transfusion in the immediate postnatal period. Thirty infants (83%) developed late anemia and required blood transfusions at a mean postnatal age of 43.3 +/- 15.7 days. Sixty-four percent of infants who had exchange blood transfusions did not develop late anemia, while 92% of infants who did not require exchange blood transfusion developed late anemia, and the difference was statistically significant (P = 0.035). Serum erythropoietin levels were determined in 8 infants immediately before simple transfusion for late anemia. The media serum erythropoietin level was 21.2 mU/ml, ranging between less than 10 to 114.2 mU/ml. We conclude that late hyporegenerative anemia is common among Rh isoimmunized infants, regardless of the intravascular intrauterine transfusion. Exchange blood transfusion was associated with less occurrence of late anemia.