title: Neonatal water metabolism: an objective postnatal index of intrauterine fetal growth.
abstract: The water metabolism of 103 newborn babies was determined over the first 10 postnatal days, by measuring water turnover rates by means of an isotope dilution technique. This technique involves the oral administration of the non-radioactive isotope of water, 2H2O, and the measurement of its urinary excretion by infrared spectrophotometry. The slope of the excretion curve after equilibration with the infant's body water was mathematically expressed as the rate constant. Using multiple obstetric and paediatric criteria, the babies were clinically classified into one of three categories, fully grown ("normal'), borderline or clearly growth retarded. The median values of the rate constants X 10(4) (h-1) for the three groups were 73.3, 85.9 and 100.2 and were highly significantly different from each other (P less than 0.0005) with no overlap of the 97% non-parametric confidence limits of each group. Neonatal water turnover increased with the clinical degree of intrauterine fetal growth retardation and within the limits of this study, this finding was unaffected by gestational age, birth weight or the neonatal environment. The results suggest that neonatal water metabolism is an objective postnatal index of fetal growth retardation.
mesh_terms: D001834:Body Water / Q000378:metabolism*; D001835:Body Weight; D005260:Female; D005317:Fetal Growth Retardation / Q000175:diagnosis* / Q000378:metabolism / Q000652:urine; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D011247:Pregnancy; D011272:Pregnancy, Multiple; D013997:Time Factors