Fetal Foot Length as a Predictor of Gestational Age

Background: Accurate estimation of gestational age (GA) is essential for obstetric care. Conventional ultrasound (US) biometric parameters may be limited in certain clinical situations. Fetal foot length (FFL) has been proposed as an alternative measurement, but its role requires further evaluation. Aim of study: To examine the association between fetal foot length and ultrasound-based gestational age, and to explore its relationship with other fetal biometric parameters in uncomplicated singleton pregnancies. Methods: This cross-sectional study included 200 pregnant women who underwent two-dimensional transabdominal ultrasound. Standard fetal biometric parameters—including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL)—were measured alongside FFL. Gestational age was determined using conventional ultrasound biometry. Correlation and regression analyses were performed to assess associations. Results: Mean FFL was 54.96 ± 15.89 mm (range: 18–85 mm). FFL showed a strong positive correlation with ultrasound-based GA (r = 0.976, p < 0.001). Linear regression analysis yielded the equation: GA (weeks) = 5.835 + 0.424 × FFL (mm), with R² = 0.952, mean absolute error of 1.02 weeks, and root mean square error of 1.50 weeks. The regression coefficient for FFL was 0.424 (95% CI: 0.411–0.438), and the intercept was 5.835 (95% CI: 5.074–6.596). Residual analysis supported model fit, but no internal or external validation was performed. FFL also correlated strongly with FL (r = 0.967, p < 0.001) and other biometric parameters. Estimated fetal weight analysis was exploratory only and demonstrated consistent correlations with FFL and standard measurements. Conclusion: Fetal foot length demonstrated a strong statistical association with ultrasound-derived gestational age and other biometric parameters. These findings reflect correlation rather than validated prediction, and clinical interchangeability was not assessed because agreement analysis was not performed. FFL may be considered a potentially useful adjunct measurement when conventional parameters are suboptimal, but further validation using independent gestational age standards and diverse populations is required before clinical application.