Beyond Traditional Biometry: The Role of Fetal Kidney Length in Third Trimester Gestational Age Assessment

Aim and background: Fetal kidney length (FKL) demonstrates consistent and proportional growth throughout the third trimester, which makes it a promising candidate for accurate gestational age (GA) estimation. This study aims to elucidate whether FKL offers distinct advantages over existing methods or if it complements them effectively in enhancing the accuracy of GA assessment. Methods: The present prospective cross-sectional study was conducted at the Department of Obstetrics and Gynecology at Acharya Vinoba Bhave Rural Hospital (AVBRH) from 2022 to 2024 among 100 normal pregnant patients attending Obstetrics and Gynecology services at AVBRH. Relevant clinical information, including maternal age, parity, medical history, and last menstrual period (LMP), was meticulously recorded for each participant. Participants underwent obstetric ultrasonography using an Aloka Hitachi Aritta machine (Hitachi Aloka Medical Ltd., Tokyo, Japan) equipped with a 3.5 MHz ultrasound transducer. Fetal biometric parameters, including FKL, biparietal diameter (BPD), femur length (FL), abdominal circumference (AC), and head circumference (HC), were measured using standardized techniques. Results: GA based on the LMP showed a very strong positive correlation with FKL (r = 0.990, p < 0.001). Strong correlations were also observed with FL, HC, AC, and BPD (all p < 0.001). There was a linear relationship between GA and the FKL. Conclusion: It can be concluded from the study that FKL is a strong, reliable indicator for determining GA. The high correlation of FKL with GA suggests its potential use in clinical settings for fetal development assessment. Clinical significance: This study encourages the integration of FKL measurements into routine obstetric ultrasound protocols, alongside traditional parameters like BPD, HC, AC, and FL. There should be the establishment of standardized protocols for measuring kidney length to ensure consistency and accuracy across different practitioners and ultrasound equipment.