As compared to other organs, in intrauterine growth retardation brain is less affected; however, forebrain weight and total lipids are reduced. Myelin quantity is reduced by 27, 17, 9 and 6% at 15, 18, 30 and 60 days after birth, respectively. Thus, intrauterine undernutrition followed by normal diet after birth affects myelination, a postnatal event. Prenatal growth retardation moderately but irreversibly impairs brain maturation, whereas the composition of myelin during maturation is close to normal (when density profile, lipid amount and the fatty acid pattern are considered).