Abstract
BACKGROUND: True umbilical cord knot (TUCK) is frequently missed in prenatal ultrasound (US), hindering standardized management and risk assessment of adverse perinatal outcomes. This study aimed to assess TUCK detection accuracy using active umbilical cord (UC) scanning and identify factors affecting prenatal visualization. METHODS: A prospective study of 378 pregnant women (11-40 weeks) was conducted. Experienced and novice physicians sequentially scanned the full UC, grading umbilical cord ultrasonic image quality (UCUIQ) as sufficient (scale 1), restricted (scale 2), or poor (scale 3). Factors affecting UCUIQ were analyzed using multiple logistic regression, and diagnostic accuracy was evaluated. Cases for diagnosis were confirmed at delivery. RESULTS: Interobserver agreement for UCUIQ grading was excellent (К = 0.979). Gestational week emerged as the primary factor influencing UC visualization (P < 0.05), with ultrasound achieving a diagnostic accuracy of no less than 89.3% for TUCK detection during the 17-26 weeks gestational period. CONCLUSIONS: Gestational week significantly influenced TUCK detection, with high accuracy at 17-26 weeks. Active UC scanning during this period improved detection accuracy of TUCK.