First-trimester diagnosis of fetal abnormalities. A report of three cases.

First-trimester sonography is used extensively for dating pregnancy and in conjunction with chorionic villus sampling. It is crucial to examine the fetus carefully, even at this early stage, since some fetal abnormalities are detectable in the first trimester. In three cases encephalocele, thanatophoric dwarf and cystic hygroma were diagnosed with sonography in the first trimester.