Prenatal development of brown adipose tissue in man. A morphometric and biomathematical study

In a series of 110 liveborn infants who died within 24 h of birth, and six 14- to 17-week-old fetuses, the development of perirenal brown fat was studied by morphometric and biomathematical methods. Brown fat was present at the 20th week of age and, taking as index of maturity the population of multilocular adipocytes, its development progressed according to a 3-parametric logistic growth function, with a half-time of 26 weeks and a tendency to asymptotic stabilization by the 35th week. Unilocular adipocytes appeared early and their low percentage (10.9%) remained relatively stable. Brown fat development in 75% of the cases of small-for-dates corresponded to that of infants with matched postconceptional age but appropriate birth weight. Abnormal cases presented whether a persistence of immature patterns or an unusual predominance of unilocular cells. No changes due to lipolysis were detected in any case.