Combining Detailed Fetal Anatomy Scanning in the NT Window Versus Early Second Trimester Scanning at 14–16 Weeks

Objectives First‐trimester ultrasound has evolved to incorporate a detailed fetal anatomy scan (FAS) with nuchal translucency (NT) screening. Many institutions use a 2‐visit protocol: NT followed by detailed FAS at 14–16 weeks. We aimed to evaluate whether integrating detailed FAS into the NT window (12 + 5 to 13 + 6 weeks) is non‐inferior in diagnostic yield to the 2‐visit protocol. Methods We enrolled 755 mixed high‐ and low‐risk pregnant women with singleton gestations into either integrated NT + FAS group (n = 243, 12 + 5 to 13 + 6 weeks) or 2‐visit group (n = 512, 14–16 weeks). All underwent follow‐up at 20–24 weeks. Scans followed ISUOG guidelines; the primary outcome was detection of fetal anomalies during detailed early scans. Non‐inferiority was defined as a margin of ≤6% difference in detection rates. Results Study groups were similar except in parity (mean 2.6 [0–9] vs. 3.1 [0–10], P = .0081 in FAS + NT and 2‐visit group, respectively). Anomalies were identified in 16 fetuses (7.5%) in the NT + FAS group and 16 (3%) in the 2‐visit group ( P = .033). Additional anomalies were detected at mid‐trimester in 2/227 (0.9%) NT + FAS and 4/496 (0.8%) 2‐visit group fetuses ( P = 1.0). The integrated approach met non‐inferiority criteria. Conclusion Detailed FAS during the final NT window week is non‐inferior to the 2‐visit approach. This integrated protocol offers earlier reassurance without compromising diagnostic accuracy.