Objective: To determine the reliability of bioelectrical impedance analysis, and to compare and contrast the anthropometric and BIA status of newborns.
Design: BIA and anthropometric parameters were compared in the few days after birth and at about 3 weeks of age.
Setting: At the maternity hospital or in a paediatric care unit.
Subjects: Small- or appropriate-for-gestational-age newborns, with birth weight below or above the 10th percentile of the reference value, respectively. Measurements were performed on 36 and 47 newborns at birth, and for a subgroup (21 and 11) again about 3 weeks later, respectively.
Results: At birth, length2/resistance was 4.3 +/- 0.6 and 6.1 +/- 1.2 cm2/omega (P = 10(-7)), and at 3 weeks of age length2/resistance was 5.0 +/- 0.6 and 5.7 +/- 0.8 cm2/omega (P = 0.11), for small- and appropriate-for-gestational-age newborns, respectively. Percentage reliability was 2.2% and 2.6% for intra- and inter-observer measurements of resistance. Importance of a correct placement of the sensor electrode was demonstrated.
Conclusions: Ease of measurement and reliability of BIA in neonates were shown. Evolution of BIA values is in agreement with the known increase in total body water linked to regrowth of cell mass in small-for-gestational-age infants. Additional study is required before BIA should be used in usual clinical setting in newborns due to the lack of prediction equation.