purpose: the pathophysiology of abnormalities associated with myenteric plexus lesions remains imperfectly understood. such abnormalities have been correlated with subocclusive intestinal conditions in children with hirschsprung's disease, cases of chronic constipation and, postoperatively, in cases of anorectal anomalies. this study evaluated abnormalities of the myenteric plexus in fetus from female rats that received ethylenethiourea. methods: female rats were exposed to ethylenethiourea on the 11th day of pregnancy (experimental group) or to 0.9% physiological solution (control group). abnormalities were only found in the experimental group. the digestive tract muscle layer was analyzed morphometrically and changes to the frequencies of nerve plexus cells and interstitial cells of cajal were evaluated, using hematoxylin-eosin, s-100 protein, neuron-specific enolase and c-kit, respectively. results: muscle and skeletal abnormalities were observed in 100%, anorectal anomalies in 86%, absent tail in 71%, short tail in 29%, duodenal atresia in 5%, esophageal atresia in 5% and persistent omphalomesenteric duct in 5%. histopathological analysis showed a thinner muscle layer associated with lower frequencies of ganglion cells and interstitial cells of cajal, in all gastrointestinal tract. conclusion: severe nerve plexus abnormalities associated with muscle layer atrophy were observed throughout the gastrointestinal tract in newborn rats exposed to ethylenethiourea.