ABSTRACT
We reviewed reports on first-trimester sonographical screening for fetal abnormalities and fetal aneuploidies. Higher incidences of spontaneous abortion or placenta previa are reported to exist in cases where the gestational sac is detected in the middle or lower portion of the uterine corpus. In multiple pregnancies, the determination of chorionicity and amnionicity must be accurately made during the first trimester of pregnancy. Reports on the usefulness of nuchal translucency measurements for screening of aneuploidies have been presented, but some investigators have reported on the very limited usefulness, especially for the low-risk population. Some of the major structural abnormalities are detectable in the first trimester and are considered to be related to aneuploidies. It is reported that early growth restriction of the fetus is related to trisomies 18 and 13. In trisomies 21, 13 and Turner syndrome, it is reported that the fetal heart rate in early pregnancy is significantly higher. Doppler velocimetry in the umbilical artery, umbilical vein, ductus venosus and maternal uterine artery is helpful for the prediction of fetal abnormalities. First-trimester sonography is very important for the early detection of fetal aneuploidies and other abnormalities.