Bioelectrical impedance analysis in small- and appropriate-for-gestational-age newborn infants.

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.

Evidence that liver microsomes of human neonates desaturate essential fatty acids.

delta 6- and delta 5-Desaturation of essential fatty acids of n-6 and n-3 series are required for the biosynthesis of polyunsaturated fatty acids (PUFAs), which are precursors of eicosanoids and constituents of membrane phospholipids. This pathway could be of special importance during the perinatal period, when PUFAs accretion in the central nervous system is very active. However, experimental evidence of delta 6- and delta 5-desaturase activities in man is very scarce, and no data are available for newborns. We report the delta 6- and delta 5-desaturase activities detected in human liver microsomes from three neonates who died from associated malformations. Radiochemical assays of delta 6- and delta 5-desaturase activities performed with reverse phase HPLC analysis of the products in the n-6 series ranged from 4.8-13.6 to 3.2-16.4 pmol substrate converted.min-1.mg-1 microsomal proteins, respectively. In the n-3 series delta 6-desaturase activity ranged from 5.3 to 12.8 pmol.min-1.mg-1. The relationships between enzyme activities and substrate concentrations suggest excess substrate inhibition for n-6 and not for n-3 fatty acids. These results demonstrate significant delta 6- and delta 5-desaturase activities in human liver of neonates, but this activity was lower than previously reported in adult humans and in mammals, especially rodents.

Brainstem conduction time abnormalities in small for gestational age infants.

Brainstem auditory evoked responses (BAER) were recorded in 89 neonates born between 32 and 40 weeks, in order to analyze the consequences of intrauterine growth retardation on brainstem conduction time. The I-V interval was measured in 28 appropriate for gestational age (AGA) infants (control group), in 24 small for gestational age (SGA) infants with maternal hypertensive disease (MHD) and in 37 SGA infants without MHD. At any gestational age, SGA infants with MHD always presented an acceleration of their brainstem conduction time as compared to the other SGA infants. For the SGA full-term twins without MHD, the brainstem conduction time was delayed. These results reflect the specific consequences on brainstem development of the various factors responsible for intrauterine growth retardation (IURG).