Ultrasonographic fetal kidney length for determination of gestational age in late second and third trimesters

Bendary, Ali A.; Aboelezz Moselhy, Shreen Naguib; Khalil, Amira E.; Elsayed, Labiba Kasem

doi:10.21608/svuijm.2025.421937.2276

Ultrasonographic fetal kidney length for determination of gestational age in late second and third trimesters

Document Type : Original research articles

Authors

Department of Obstetrics & Gynecology, Faculty of Medicine, Benha University, Benha, Egypt.

10.21608/svuijm.2025.421937.2276

Abstract

Background: Accurate gestational age (GA) determination is vital for managing obstetric care but becomes challenging in the late second and third trimesters due to increasing variability in conventional fetal biometrics.
Objectives: This study investigates fetal kidney length (FKL) as a potential parameter for reliable GA estimation during this period.
Patients and methods: A cross-sectional study was conducted on 100 pregnant women with singleton pregnancies and certain dates, stratified into four gestational groups (n=25 per group). All participants underwent ultrasonography to measure FKL, biparietal diameter (BPD), femur length (FL), and abdominal circumference (AC).
Results: A strong positive correlation was found between all biometric parameters and different gestational ages. Fetal kidney length demonstrated an exceptionally strong and statistically significant correlation with gestational age (r=0.899, p<0.01), which was comparable to AC (r=0.900) and FL (r=0.897), and superior to BPD (r=0.671). The mean FKL increased predictably from 31.0 ± 6.03 mm at 24 weeks to 42.0 ± 4.0 mm at 36 weeks, with a growth rate of approximately 2.0 mm every three weeks. Paired t-test analysis showed no significant difference between the actual GA and the GA estimated by FKL (p=0.489), confirming its accuracy.
Conclusion: Fetal kidney length exhibits a strong, linear correlation with gestational age and serves as a highly reliable and accurate biometric parameter for GA estimation in the late second and third trimesters, offering a valuable adjunct to established methods.

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