Ultrasonic determination of gestational age by assessment of fetal kidney size in the third trimester in southwest Nigeria.

OBJECTIVE: To determine the strength of association between fetal kidney measurements and gestational age (GA) in third-trimester pregnancies. METHODS: In a cross-sectional study in Ile-Ife, Nigeria, women in the third trimester of a singleton pregnancy who were sure of the date of their last menstrual period or had an early pregnancy scan were recruited consecutively in 2012. Standard biometric measurements were taken, along with fetal kidney length (FKL), anteroposterior diameter (FKAPD), and transverse diameter (FKTD). Fetal kidney volume (FKV) was calculated via the ellipsoid formula. Data were analyzed by Pearson correlation and multivariate linear regression. RESULTS: In total, 470 women were recruited. Compared with standard biometric parameters, renal parameters showed better correlation with GA. Among the standard parameters, femur length showed the strongest correlation with GA. FKL and FKV showed stronger positive correlation with GA as compared with FKTD and FKAPD. In multivariate linear regression modeling, FKL alone predicted GA with accuracy of ±10.1 days, whereas a combination of standard and kidney parameters predicted GA with better accuracy of ±8.0 days. CONCLUSIONS: Compared with standard biometric parameters, fetal renal parameters correlated better with GA in the third trimester. Among the renal parameters, FKL correlated most strongly with GA.