ABSTRACT
Nine female pregnant rats were treated with single dose (30mg/kg) of 5-fluorouracil on 12th day of gestation. Gross defects in developing brain of rat fetuses were observed. 5-Fluorouracil is an antineoplastic drug, which has not been adequately studied. 5-FU induced about 5% mortality with significant reduction in body weight and various dimensions of the developing brain (p<0.001). Macroscopic findings of the developing brain revealed microcephaly, regression or absence of olfactory lobe and obliteration of the various fissures on the dorsal and ventral surfaces of the brain. Neuroembryopathic effects of 5-FU is more marked when given in late phase of gestation. So, it is advisable that the drug should be avoided during this period of pregnancy.