Diagnosis of GM1 gangliosidosis (OMIM 230500) is usually based on the presence of physical signs of storage such as coarse facial features, corneal clouding, cherry red macula, hepatosplenomegaly and skeletal dysostosis. More rarely it can present as nonimmune hydrops. We describe a male patient with GM1 gangliosidosis born to healthy first-cousin parents of Indian Asian descent. The disease was recognized on the basis of diffuse vacuolization of cyto- and syncytiotrophoblasts, stromal cells and amniocytes on histological analysis of the placenta. The placental examination was prompted by the prenatal detection of intrauterine growth retardation (IUGR) and oligohydramnios at 32 weeks of gestation. The diagnosis of GM1 gangliosidosis was supported by both biochemical and molecular data. The beta-galactosidase enzymatic activity on leukocytes was severely reduced, while the neuraminidase activity on fibroblasts was normal, thereby excluding galactosialidosis. The molecular analysis of the beta-galactosidase gene (GLB1) revealed a previously unreported splicing mutation (IVS1+2 insT) in homozygous state. Our case further illustrates the value of histological examination of the placenta in the diagnosis of lysosomal storage disorders and shows that either hydrops or IUGR can be presenting features of GM1 gangliosidosis in the neonatal period.