The relation between newborn hemoglobin F fractions and risk factors for sudden infant death syndrome

The aims of this study were to determine and compare fetal hemoglobin (HbF) fractions at birth in newborns exposed and not exposed to selected factors that have been reported to increase the risk of sudden infant death syndrome (SIDS). Previous studies have implicated HbF in the etiology of SIDS by finding higher fractions in infants dying from SIDS compared to age-matched control infants. We performed a cross-sectional study using high-performance liquid chromatography to measure HbF fractions in newborn cord blood samples. Exposure to selected risk factors for SIDS was assessed through review of medical records. Six hundred thirty-three infants born at Via Christi Regional Medical Center-St Francis Campus, Wichita, Kan, from February 28 through August 5, 1997. Hemoglobin F fractions at birth were compared in newborns exposed and not exposed to selected risk factors associated with increased incidence of SIDS. Mean HbF fractions were significantly higher in preterm newborns of mothers who smoked and in term newborns with intrauterine growth restriction, pregnancy weight gain less than or equal to 9 kg, and pregnancy complications associated with reduced placental blood flow. An elevated newborn HbF fraction, defined as 77% or greater, was significantly associated with maternal smoking, maternal anemia, intrauterine growth restriction, and pregnancy complications associated with reduced placental blood flow. This study suggests a possible mechanism (HbF) by which previously identified factors may increase the risk of SIDS.