Fetal malformations induced by a maternal diet rich in a vitamin A palmitate complex (Ortosan) in the rat. Ortosan is a compound composed of vitamin A in its esterified form, vitamin A palmitate. Previous findings have demonstrated teratogenic activity of this product in a number of animal species. The present study was aimed at investigating the hypothesis that a maternal diet rich in Ortosan might be associated with the occurrence of abnormalities in the offspring. Fifty Wistar rats were randomized into a control group fed ad libitum (group A) and a group fed ad libitum and given the compound Ortosan (group B). Dams were fed with a balanced diet containing 5,000 IU/kg vitamin A, from day 0 to day 10 of pregnancy. Body weight gain was significantly lower in dams fed with Ortosan compared to controls. In group B, 7 out of 28 fetuses presented malformations (20.6%) and 3 had a hydrocephalic malformation. A clear correlation was found between abnormal fetuses and maternal body weight gain. Our study suggests that Ortosan can produce teratogenic effects on fetal development, even at the relatively low dose given in our experimental study. In addition, we hypothesize that a low body weight gain in the dams due to an imbalance in body nutrient intake (vitamin A) may be responsible for this teratogenic activity. Further studies are needed to elucidate the effect of different dosages of a vitamin A palmitate complex in animal diets and its potential for developmental malformations.