RENAL DEVELOPMENTAL ARREST IN SUDDEN-INFANT-DEATH-SYNDROME

Investigations linking sudden infant death syndrome (SIDS) and type II intrauterine growth retardation (IUGR) have thus far failed due in pa rt to technical limitations. Recently developed stereological methods for the unbiased estimation of total nephron number in the human kidne y are capable of detecting deviations from normal values of greater th an 10%. We compared the total number of nephrons in the kidneys of 24 SIDS victims with those from 16 controls with the same age range. Mean nephron number was significantly (P < 0.001) reduced in ex-IUGR SIDS cases (birthweight under the 10th centile, n = 9, mean number 635, 000 , range 327, 000-1,010,000) in comparison with controls (903, 000, 740 ,000-1,060,000). A similarly significant (P < 0.01) reduction in the ' 'normal birthweight'' SIDS group (birthweight over 10th centile, n = 1 5, 690,000, 361,000-1,040,000) was found. This hitherto unreported ren al developmental arrest may be only one manifestation of a general, so matic developmental defect, reflecting adverse intrauterine conditions ; other organ systems, similarly critical to homeostasis may be compar ably affected. The findings, although not proposed as direct cause of SIDS, may represent a potential explanation for the recognized associa tion of IUGR and SIDS, and provide-we believe-the first quantitative e vidence of intrauterine growth retardation in, at kast a number of, ch ildren of average birthweight.