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Transabdominal sonography has been, for the past two decades, used as an effective diagnostic and research tool in obstetrics. Its use in the first trimester is relatively limited and mostly diagnostic in nature. The introduction of the higher frequency transvaginal transducer probe, with its higher resloution of the images, opens new possibilities to study early gestation. There is a need for techniques which will allow an early diagnosis to be made in high risk patients of early pregnancy failure, preferably with such certainty that a more active line of management can be pursed if so desired. A total of 164 transvaginal scans were performed from 4 to 12 weeks` gestation in the high risk patients of early pregnancy failure. The sequential appearance of 9 embryonal structures or functions were examined: (1) the gestational sac appeared in week 4: (2) the fetal pole with detectable heart beat was first seen in week 5~6: (3) the yolk sac was present from week 6~7:(4) the single unpartitioned ventricle in the brain, the amnionic sac and the body stalk or umbilical cord marked week 7: (5) the falx cerebri and fetal motion appeared during week 8, respectively in continued pregnancy. A sac greater than 26 mm in diameter without fetal heart beat is a poor prognostic sign. Before a live embryo is visualized in the intrauterine gestational sac, no sonographic features were found to be reliable in differentiating viable from nonviable pregnancy (presenting as an empty gestational sac) on a single sonographic examination. Serial vaginal sonography is effective and efficient in the diagnosis and management of early pregnancy failure.
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