Brain: body ratio and conceptional age in vascular-induced intrauterine growth retarded rabbits.

Vascular induced intrauterine growth retardation (IUGR) was achieved by total ligation of approximately 30% of the placental vessels to half the fetuses in the last third of gestation in pregnant rabbits. A correlation between brain weight, body weight and head circumference was established in fetuses and rabbit pups in the perinatal period. The brain:body ratio in restricted IUGR animals was significantly higher than their homologous normal controls. A cephalization index based on the brain:body ratio is proposed to assess adverse effects on brain maturity in the presence of IUGR induced by placental insufficiency.