Non-immune hydrops fetalis caused by beta-glucuronidase deficiency (mucopolysaccharidosis VII). Study of a family with 3 affected siblings. We describe a family case of beta-glucuronidase deficiency with 3 consecutively affected siblings. The three fetuses showed hydrops at a very early stage. In the first and second pregnancy the hydrops was visible on ultrasound scan in the first trimester. In the second pregnancy this was highly suggestive for recurrence. The diagnosis of mucopolysaccharidosis type VII was suggested after pathologic examination of the first fetus and placenta, and confirmed by deficient beta-glucuronidase activity in cultured skin fibroblasts. In the second, as well as in the third pregnancy a prenatal biochemical diagnosis was possible on cultured chorionic villus cells. The third pregnancy was terminated before hydrops was visible on ultrasound scan. Pathologic findings in the 3 fetuses were similar. Vacuolated macrophages were found in all tissues, but were most prominent in placenta, liver, lymph nodes and bone marrow.