Frequency and Importance of Incomplete Screening Fetal Anatomic Sonography in Pregnancy

Objectives: To determine (1) how often routine screening fetal anatomic sonography fails to completely visualize fetal anatomy; (2) the proportion of women with incomplete ultrasound examinations who are recommended for repeat screening and then undergo repeat sonography; and (3) how often abnormal fetal anatomy is detected on repeat sonography.

Methods: We conducted a retrospective cohort study at a high-volume academic obstetric ultrasound center. Participants were 16,300 women at 17 through 21 weeks' gestation with a singleton pregnancy presenting for screening anatomic sonography between January 2009 and December 2013. Main outcome measures were (1) incomplete visualization of anatomy at initial screening sonography; (2) among women with incomplete but otherwise normal initial screening ultrasound examinations, recommendation for and performance of repeat sonography; and (3) among women undergoing repeat sonography, discovery of abnormal fetal anatomy within anatomic components that were previously incompletely visualized.

Results: The mean maternal age ± SD was 30.8 ± 6.3 years, and the mean gestational age was 18.8 ± 1.0 weeks. Among 16,300 initial screening ultrasound examinations, 2157 (13.2%) had incomplete visualization of fetal anatomy. Of those women eligible for follow-up, 91.5% were recommended for repeat screening, of whom 92.8% had a subsequent examination. Of 1560 repeat screening ultrasound examinations, 8 (0.5%) showed an abnormality in the components of anatomy that were previously visualized incompletely.

Conclusions: In this large single-center study, incomplete visualization was common in screening fetal anatomic ultrasound examinations. Recommendations for repeat imaging were nearly universal, but abnormal fetal anatomy was infrequently discovered on repeat screening.