USG can diagnose all except:

D i.e. Down's Syndrome In anencephaly, absece of vault. In NTD, presence of meningo-myelocoel & In placenta pre location of placenta seen by USG confirms the diagnosis. Although on prenatal U/S increased nuchal fold thickness, and reduced length of femur & humerus are suggestive of Down's syndrome but the diagnosis is confirmed by chromosomal study (trisomy of 21st autosome) either by amniocentesis or chronic villous sampling.