The high resolution, safety and ease of performance make ultrasound the procedure of choice for routine ultrasonography in the first half of pregnancy as a standard of obstetric care. Transvaginal ultrasound has revolutionized the diagnosis and management of early pregnancy. Pregnancies can be detected earlier compared with abdominal ultrasound, patients reassured by showing normal development, accurate gestational age determination, sufficiently early characterization of multiple pregnancy, early diagnosis of lethal anomalies and screening of chromosomal defects can be done with first trimester ultrasonography. Furthermore, recent introduction of three-dimensional and fourdimensional ultrasounds combined with the transvaginal approach has produced more objective and accurate information on embryonal and early fetal development and made it possible to visualize fascinating aspects of embryonic differentiation.
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