Normal fetal hemoglobin levels in the sudden infant death syndrome

It has been reported that infants who die of the sudden infant death syndrome (SIDS) have elevated fetal hemoglobin levels. To test this hypothesis, we determined the level of fetal hemoglobin in dead and living infants in three different laboratories by three methods: high-performance liquid chromatography, polyacrylamide-gel electrophoresis, and cell-based immunofluorescence assays for fetal hemoglobin-containing red cells (F cells). Our infant study population consisted of 67 infants who had died of SIDS, 22 control infants examined at autopsy, and 80 living infants. The fetal hemoglobin level was not higher in the infants who had died of SIDS than in the control infants for any age group analyzed. Immunofluorescence assays for F cells were also performed in blood samples from 105 mothers of infants who had died of SIDS, 55 adult female controls, 52 fathers of infants who had died of SIDS, and 67 adult male controls. The percentage of fetal hemoglobin-containing red cells in the parents of infants who had died of SIDS was not statistically different from that in sex-matched adults in the control groups. We conclude that elevated fetal hemoglobin levels in infants or their parents are not suitable for use as indicators of the risk of SIDS in the infants. Furthermore, the fetal hemoglobin level is not useful as a postmortem marker of an infant's having died of SIDS.