Estimation of Third-Trimester Gestational Age Using Ultrasonographic Fetal Renal Measurements: A Cross-Sectional Study

Abstract

Introduction: Accurate estimation of gestational age in the third trimester is challenging due to reduced reliability of conventional fetal biometric parameters such as biparietal diameter, head circumference, abdominal circumference, and femur length. Alternative sonographic markers may improve late gestational dating accuracy.
Methods: This cross-sectional observational study was conducted between December 2020 and November 2022 in the Armed Forces Medical College, Pune. The study included pregnant women with singleton pregnancies. All participants had uncomplicated pregnancies and were between28 and 40 weeks of gestation at the time of enrolment. Ultrasonographic measurements of fetal kidney length and renal volume were obtained along with conventional fetal biometric parameters. Gestational age derived from a reliable last menstrual period was used as the reference standard. Pearson’s correlation coefficient was used to assess the correlation between renal measurements and conventional biometric indices with gestational age.
Results: Ninety-six pregnant women were included in the study. The mean maternal age was 28.35 ± 5.05 years. Among 96 patients, the correlation of mean kidney length with last menstrual period-derived gestational age (GA) was strongest (r=0.875). Among the conventional biometric indices, GA from abdominal circumference showed a strong correlation (r=0.861), followed by femur length–based period of gestation (r=0.820), head circumference–based gestational age (r=0.804), and biparietal diameter-based gestational age (r=0.723).
Conclusions: Fetal kidney length can be a reliable and independent parameter for estimating gestational age in the third trimester and can be incorporated as a useful adjunct in routine obstetric ultrasonography.