Fetal Kidney Length in Gestational Age Prediction: A Comparative Study

Estimation of accurate gestational age is critical in perinatal care. Traditional fetal biometrics measured via ultrasonography face limitations, especially in the third trimester. Fetal Kidney Length (FKL) has emerged as a promising biometric parameter associated with advanced Gestational Age (GA). This study aimed to examine the diagnostic accuracy of FKL in comparison with traditional parameters in late pregnancy to optimize patient management and outcome.

A cross-sectional study enrolled 124 low-risk pregnant women with confirmed dating at 28-40 weeks of gestation. For every participant, two sets of data were collected: demographics (age, gravidity, date of last menstrual period) and fetal biometric parameters [Biparietal Diameter (BPD), Head Circumference(HC), Abdominal Circumference(AC), Femoral Length (FL), Amniotic Fluid Index(AFI), Estimated Fetal Weight (EFW), and Fetal Kidney Length (FKL)] including the length and width were calculated. Pearson's Correlation coefficients measured the strength of the association between GA and ultrasonic parameters.

The mean KL for right and left (RKL, LKL) was 3.94±0.36 vs. 3.95±0.37 cm; p=0.84. FKL showed positive correlations with GA (r=0.54,0.52), p<0.001 for RKL, and LKL with determination coefficient r2= (0.29,0.27), respectively. GA was positively and strongly correlated to HC, AC, and FL with a correlation coefficient of 0.77, 0.76, and 0.73; p<0.001, respectively. The determination coefficient for the HC, AC, and FL were 0.29 and 0.27, respectively.

FKL showed a moderate link to GA during the third trimester; it did not surpass traditional fetal biometric parameters. Still, FKL measurement had advantages: consistent values, independence of feto-maternal condition, and non-invasiveness and acceptability. These qualities recommended FKL for integration into routine prenatal care as a supplementary metric when other parameter calculations are challenging. Further research is warranted to examine FKL performance when combined with other biometrics and explore its diagnostic and prognostic applications.