Mucopolysaccharidosis type VII (MPS VII) was diagnosed in a case of severe fetal hydrops. beta-glucuronidase deficiency was demonstrated in the amniotic fluid, which was obtained at 25 weeks of gestation, and in the fibroblasts of the child, which were cultured after fetal death in the 26th week of gestation. In the amniotic fluid the two-dimensional electrophoresis pattern of glycosaminoglycans was in agreement with MPS VII. Based on these results, prenatal diagnosis could be offered to the couple for the next pregnancy.