Fetal Kidney Diameter as a Parameter for Determination of Fetal Gestational Age in Apparently Healthy Nigerian Women

Background: Accurate determination of gestational age (GA) is vital in obstetric management, as incorrect dating may result in preterm or post-term delivery, both of which are associated with adverse perinatal outcomes. Conventional ultrasound parameters such as Biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) are commonly used for gestational age estimation; however, their accuracy declines in the late second and third trimesters. This study investigated the relationship between fetal kidney antero-posterior diameter (APD) and gestational age and sought to establish baseline reference values among Nigerian women.

Materials and methods: A prospective cross-sectional study was conducted among 208 apparently healthy pregnant women between 20 and 40 weeks of gestation who attended the Radiology Department of the Federal Medical Centre, Jalingo, Taraba State. Standard fetal biometric parameters (BPD, HC, AC, and FL) as well as fetal renal antero-posterior diameters were measured using a GE Logic 7 ultrasound machine equipped with a 3.5 MHz convex transducer. Statistical analyses, including Pearson correlation and linear regression, were performed using SPSS version 30.0 to determine the strength of association between gestational age and fetal kidney diameter and to derive regression equations for gestational age prediction.

Results: The results showed mean right and left fetal renal antero-posterior diameters of 19.87 ± 4.88 mm and 20.09 ± 4.94 mm, respectively. Both parameters demonstrated a strong positive correlation with gestational age (r = 0.928 and r = 0.927, p < 0.001) and a high coefficient of determination (R² = 0.86). The regression model indicated that fetal kidney antero-posterior diameter increases by approximately 0.74 mm for each advancing week of gestation.

Conclusion: The fetal renal antero-posterior diameter correlates strongly with gestational age and can serve as a reliable adjunct parameter for gestational age estimation, particularly when conventional biometric indices are limited. The established baseline reference values provide useful population-specific data for Nigerian women and support broader clinical application in obstetric sonography.