The tests can be used to check for conditions such as Down syndrome , spina bifida , cleft palate , Tay Sachs disease , sickle cell anemia , thalassemia , cystic fibrosis , and fragile x syndrome . The aim is to detect birth defects such as neural tube defects , Down syndrome , chromosome abnormalities , genetic diseases and other conditions , such as spina bifida , cleft palate , Tay Sachs disease , sickle cell anemia , thalassemia , cystic fibrosis , and fragile x syndrome .