Shift from fetal to adult hemoglobin production in a preterm infant after exchange transfusion: a quantitative approach.

To evaluate the quantitative aspects of the shift in production from fetal hemoglobin (HbF) to adult hemoglobin (HbA), the HbF and HbA mass were estimated in a preterm infant (gestational age 29 weeks) for 22 weeks after an exchange transfusion the second day of life, leading to an initial HbA% of 100. Up until the estimated time of delivery, the HbA mass declined continuously, at a rate corresponding to a survival time of the transfused HbA erythrocytes of 100 days, and the rise in total hemoglobin mass could be ascribed solely to a rise in the HbF mass. HbF% maximum was reached 3 weeks before HbF mass maximum, and, thus, the HbF% and HbA% time courses gave no basis for evaluation of the production/destruction balance of HbF and HbA erythrocytes. The applied quantitative approach seems to be a useful additional procedure for evaluating the switch from HbF to HbA production and for estimating HbA erythrocyte survival time in preterm infants.