Negative Predictive Value of Rapid Emptying of the Fetal Bladder (≤40 Min and Post-void ≤2 mm) on Major Chromosome Aneuploidies at 11-14 Gestational Weeks: A Prospective Diagnostic Accuracy Study

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.