Objectives: The objective of this study was to determine the extent to which normal fetal anatomy can be detected between 11- and 14-week scan by sonographers in the US.
Study design: In a prospective cross-sectional study, 223 unselected women underwent a detailed assessment of fetal anatomy at 11 to 13 and 6/7 weeks by sonographers with transabdominal and/or transvaginal transducers. Thirty-seven structures were examined. Two groups were identified: group I: 121 patients between 11 and 12 weeks, and group II: 102 patients between 13 and 14 weeks.
Results: Structures other than the posterior fossa, heart, genitalia, and the sacral spine were seen between 64% to 99% for group I, and 72% to 98% for group II. The following structures were detected with statistically significantly higher rates in group II compared with group I: cerebellum, posterior fossa, face, 4-chamber view left ventricular outflow tract, aortic arch, ductal arch, kidneys, and genitalia. Comparing the patients of group I and group II, the transvaginal scans yielded a higher detection rate of structures than do the transabdominal scans.
Conclusion: Anatomic surveys between 11 and 14 weeks can be performed by sonographers with good detection rates of most structures. Using the vaginal probe compared with the abdominal probe improved the detection rate at 13 to 14 weeks as well as 11 to 12 weeks. If early fetal structure evaluation is to become customary in the US, the present practice of experienced and trained sonographers to scan such patients can be maintained.