Evaluation of Fetal Bladder Emptying During the 11-14 Weeks' Ultrasound Examination as a Negative Predictive Marker for Chromosomal Abnormalities

Template-Based Brief Summary (Sağlık Profesyonelleri İçin) Study Title: The Negative Predictive Value of First-Trimester Fetal Bladder "Rapid Emptying" (≤40 minutes and post-void ≤2 mm) for Major Chromosomal Aneuploidies: A Prospective Diagnostic Accuracy Study. Purpose: To evaluate whether the dynamic phenotype of rapid bladder emptying at 11-14 weeks reduces the likelihood of major chromosomal abnormalities (particularly Trisomy 21) compared to fetuses without this phenotype. Design: Single-center, prospective observational cohort. Population: 270 singleton pregnancies between 11+0 and 14+0 weeks. Procedures: Real-time sagittal ultrasound observation for 40 minutes. Documentation of bladder emptying time and post-void longitudinal bladder diameter. Concurrent measurement of CRL, NT, ductus venosus waveform. Gold standard confirmation with cfDNA or invasive karyotyping in high-risk cases. Primary Endpoint: Negative predictive value (NPV), ROC-AUC, sensitivity/specificity for aneuploidy detection. Secondary Endpoints: Rate of invasive testing, performance in combined models with cfDNA and biophysical markers, Net Reclassification Index. Duration: 5 months (08/2025 - 01/2026). Potential Impact: If validated, the rapid emptying phenotype may serve as a low-risk marker, reduce unnecessary invasive procedures, and refine first-trimester screening algorithms.