(951) Early Anatomic Ultrasound to Detect Fetal Anomalies in High Risk Patients at 12-14 Weeks Gestation

Objective: Detailed evaluation of the fetus in the late first trimester is now possible. We report on the outcomes of a cohort of high-risk patients who underwent detailed fetal evaluation at 12-14 weeks’ gestation (WG).

Study Design: Patients referred for early anatomy scans underwent detailed evaluation using a protocol based on AIUM practice parameters. Outcomes of all referred patients from 01/2021 through 07/2024 were collected. Variables included referral indications, maternal age, gestational age, need for endovaginal scan, detection of minor and major anomalies, genetic testing results, and outcomes based on second-trimester anatomy scan, fetal echo, or at birth.

Results: In all, 217 patients were included. Indications included prior pregnancy with genetic or structural anomalies (34%), maternal age or patient request (14%), abnormal screening (10%), suspected abnormalities on a routine scan (8%), teratogen exposure (7%), perinatal risk factors (5%), and complicated twins (1%). Median gestational age was 13+2 weeks’ (IQR 1+1), 1.4% were twins and 2.8% required an endovaginal scan. In all, 55 (25.3%) had abnormal results: 36 of these were confirmed, 1 minor finding was not confirmed, 3 had fetal demise, 14 terminated, and 1 pregnancy is ongoing. Terminations without confirmation were for severe limb anomalies (2), acrania (1), abnormal CVS (8), sirenomelia (1), and bladder outlet obstruction (2).  In the 162 (74.6%) cases with normal findings, 139 were confirmed normal at 20 WG or birth, 2 had mild pelviectasis at 20 WG, 4 terminated for CVS abnormalities*, 12 had follow-up elsewhere, and 5 have ongoing pregnancies.  No major abnormalities were detected, and the only false positive result was a suspected persistent left superior vena cava that was not confirmed on fetal echo.

Conclusion:

Dedicated anatomic evaluation at 12-14 weeks’ gestation in high-risk patients has a high yield of abnormal findings and a high accuracy. For patients at high-risk, this option can provide earlier detection of significant anomalies as well as earlier reassurance/counseling.