Assessment of embryonic anatomy at 6-8 weeks of gestation by intrauterine and transvaginal sonography

Our purpose was to compare the ultrasound visualization of the early first-trimester embryo using transvaginal and intrauterine sonography. In all, 32 women about to undergo therapeutic abortion at 6-8.9 weeks gestation were studied using a specially developed catheter-based, high-resolution, real-time miniature (2.4 mm outer diameter) ultrasonography transducer (20 MHz). Before the intrauterine sonographic procedure was performed, transvaginal sonographic assessment of the embryo was conducted. The parameters evaluated included the ability to visualize anatomical structures and a subjective assessment of the overall image clarity. The ability to view most organs was better with intrauterine sonography compared to transvaginal sonography, and this was especially true for the brain, spine, heart, liver, midgut herniation, extremities, and sacral tail. Moreover, it was possible to obtain finer image quality of very small embryonic structures with intrauterine sonography than with transvaginal sonography. Stomach, spleen, kidney, and bladder could not be depicted with both techniques. One cystic hygroma was diagnosed at 7 weeks 6 days using intrauterine sonography, but not with transvaginal sonography. Intrauterine sonography may provide additional information on the visualization of anatomical structures of the embryo in the early first trimester of pregnancy. In this limited series, one case of cystic hygroma was demonstrated and, thus, there is a potential for its use in the early detection of embryonic malformation. These results suggest that intrauterine sonography may be a valuable tool in imaging the early first-trimester embryo, complementing and not replacing transvaginal sonography in high-risk pregnancies.