TY - CHAP M1 - Book, Section TI - Ultrasound of the Fetus at 11 to 18 Weeks A1 - Monteagudo, Ana A1 - Agten, Andrea Kaelin A1 - Rebarber, Andrei A1 - Timor-Tritsc, Ilan E. A2 - Fleischer, Arthur C. A2 - Abramowicz, Jacques S. A2 - Gonçalves, Luis F. A2 - Manning, Frank A. A2 - Monteagudo, Ana A2 - Timor, Ilan E. A2 - Toy, Eugene C. PY - 2017 T2 - Fleischer's Sonography in Obstetrics and Gynecology: Textbook and Teaching Cases, 8e AB - The anatomical survey, as well as the understanding of the developmental anatomy and detection rates of fetal anomalies, has evolved over the last 30 years as the result of more advanced and sophisticated ultrasound technologies. Over the last 25 years, 18 weeks has been considered by many to be the ideal or “gold-standard” gestational age to perform the first, and at times the only, anatomical survey. There are numerous advantages to performing the scan at this gestational age: the fetus is large enough to be imaged easily using transabdominal (TA) sonography, and most anomalies are present and can be detected. The disadvantage of using this gestational age for the anatomical survey is that maternal body characteristics such as abdominal obesity, uterine fibroids, and fetal position can at times preclude adequate imaging of the fetal structures, which can result in an incomplete scan. This, in turn, necessitates a follow-up scan. This need for follow-up scans has resulted in a gradual shift of the 18-week anatomy scan to be performed at 20 to 22 weeks. Therefore, the “18-week anatomy scan” has become a brand name for the sometimes only detailed anatomical survey that in many practices is carried out typically at around 20 weeks or anytime between 18 and 22 weeks of gestation. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/11/07 UR - obgyn.mhmedical.com/content.aspx?aid=1151031201 ER -