Fetuses with degenerative neurological disorders or metabolic diseases rarely exhibit sonographic abnormalities. As a result, prenatal diagnosis, when available, requires invasive testing. Prenatal diagnosis of spinal muscular atrophy (SMA) can be made by testing chorionic villi or amniocytes. Indirect genotype analysis by use of single- and multi-locus polymorphic microsatellites of the region 5q11.2-q13.3 is used. We present two cases of SMA that manifested at 11 and 16 weeks' gestation by the presence of abnormal ultrasound findings. Each case also had abnormal maternal serum screening.