The problem of hemoglobin switching in premature infants and IUGR infants.

Understanding the hemoglobin switching regulation mechanism in extremely premature infants is particularly important for understanding the extrauterine adaptation of the infants. In this study, we sought to identify factors influencing oxygen affinity in fetal blood and neonatal blood and obtained these results. (1) Aging is required for hemoglobin switching. (2) Switching in premature infants (27 to 32 weeks) is delayed at least 3 weeks in comparison with full-term infants. (3) A delay in the switching of fetal hemoglobin to adult hemoglobin was confirmed in IUGR (intrauterine growth retardation) infants. However, there is a compensatory increase in 2, 3-DPG for adaptation after birth. (4) A delay in 2, 3-DPG increase was observed in RDS (respiratory distress syndrome) infants, and oxygen affinity remained high.