Smith-Lemli-Opitz syndrome is a rare autosomal recessive genetic disorder which diagnosis is usually made postnatally. We describe a case of a prenatal diagnosis based only on specific ultrasound findings: intra-uterine growth retardation with facial dysmorphia, polydactyly and genital anomalies. We suggest giving more consideration to the ultrasound scanning for the diagnosis of the syndrome in the prenatal period.