Differential growth between the fetal brain and its infratentorial part.

From 298 normal fetuses, we established normative curves of the development of the brain in relation to gestational age and to body weight. Means and standard deviations were calculated. There exist good curvilinear relationships, expressed by polynomial models, between brain weight--body weight and brain weight--gestational age with a wider scatter in large fetuses. These results confirm literature data. Subsequently, fresh and fixed brain weights were analysed. In addition, the development of the infratentorial part of the brain was studied with the same methods and showed close relationship with age and total brain weight. The ratios: infratentorial weight/total brain weight, brain stem/total brain weight and cerebellum/total brain weight were expressed as percentages. After 20 weeks, the cerebellar growth rate was higher than that of the brain stem.