Sexual dimorphism and postnatal growth of intrauterine growth retarded rats.

The intrauterine growth retardation (IUGR) is a complex phenomenon since it causes variability in postnatal growth responses. The aim of the present study was to analyze the effects of lactational rehabilitation on body and cranial growth and sexual dimorphism in IUGR rats. IUGR model was carried out by means of uterine vessels bending in pregnant rats at the first day of pregnancy. Control and sham-operated animals were also included. During suckling, IUGR and sham-operated pups were cross-fostered to a control dam. The animals were x-rayed every four days, from birth to weaning. Body weight and length, and neural and facial variables were measured. The reduced placental blood flow delayed growth in pups. Facial growth was more impaired than the neural one. An incomplete catch up growth was found, since males reached sham values only in neurocranial height and females--except facial length and width--were similar to sham. Because of sex differences in growth recovery, normal sexual dimorphism in body and craniofacial pattern was not expressed in the IUGR group. This study suggests that reduced uteroplacental blood supply in the rat interferes with the full expression of normal dimorphism based on gender and confirms the impact of IUGR on postnatal growth.