Aim: This study tested the hypothesis that, within a few hours of delivery, cardiorespiratory measure taken during feeding provides markers of group differences related to birth weight. A secondary hypothesis was that high-frequency heart period variability would be related to underlying differences in autonomic control associated with birth weight.
Methods and subjects: One hundred four term infants in the lowest, middle, and highest birth weight quintiles were enrolled. Exclusion criteria were evidence of drug abuse, congenital anomalies, Apgar scores less than 7 or admission to the neonatal intensive care unit. Within 96 h of delivery, heart and respiratory rates, blood pressures and heart period variability were measured before, during and after feeding.
Results: Term babies in the lowest quintile of birth weights have lower heart rates prior to feeding but greater increases in heart rate during the early postprandial period. Assessments of high-frequency heart period variability suggest that small term infants have greater parasympathetic tone before feeding and more sustained parasympathetic withdrawal following feeding.
Conclusion: Measurements of cardiorespiratory functions before and after feeding are related to birth weight and may provide markers that can help identify the most vulnerable of infants with small size at birth.