Fetal Structural Anomalies and Vasa Previa Newly Identified After an Unremarkable Mid‐Trimester Systematic Ultrasound Screening: Clinical Significance and Follow‐Up Findings in 47 Cases

BACKGROUND: Some fetal structural anomalies and cases of vasa previa may not be detectable until after mid-trimester ultrasound screening. This study evaluated the spectrum, sonographic features, and perinatal outcomes of these newly detected abnormalities. METHODS: We retrospectively reviewed 14 579 singleton pregnancies that underwent standardized mid-trimester ultrasound screening with no structural abnormalities detected at that time. Among these, 47 fetuses had anomalies newly identified before delivery. One additional pregnancy, in which multiple malformations were already detected at mid-trimester screening, was encountered during the same period. Because this case did not meet the inclusion criterion of an unremarkable mid-trimester scan, it was not included in the primary cohort and is described separately. RESULTS: The detection proportion was 3.22 per 1000 pregnancies (47). Digestive and hepatobiliary anomalies accounted for 25.5% (12), followed by central nervous system anomalies 23.4% (11). Vasa previa was diagnosed in three pregnancies 6.4% (3). A total of 14 pregnancies were terminated. Four live-born infants died during the neonatal period; 21.3% (10) underwent surgery. A total of 8 of 10 surgically treated infants survived to hospital discharge. The overall survival to discharge was 61.7% (29). CONCLUSIONS: Supplementary ultrasound after mid-trimester screening can identify additional fetal structural anomalies and vasa previa and may inform prenatal counseling, delivery planning, and neonatal management.