Estimating Gestational Age in the Third Trimester: The Role of Fetal Kidney Length

Accurate gestational age is essential for effective obstetric care, managing pregnancy and preterm labor. Ultrasound, which uses fetal biometric measurements, is a dependable method for estimating gestational age. The current study focused on estimating gestational age in the third trimester by measuring fetal kidney length and comparing it with gestational age obtained from other biometric parameters and the last menstrual period (LMP).

A nine-month prospective study was conducted from September 2016 to May 2017, involving 200 women in their third trimester. Ultrasound measurements of kidney length, along with other biometric parameters (bi-parietal diameter, head circumference, abdominal circumference, and femur length), were recorded and analyzed.

The results demonstrated a strong positive correlation between fetal kidney length (FKL) in millimetres and gestational age in weeks, with a Pearson's correlation coefficient of 0.87, indicating significant results.

To summarize, a linear relationship occurs between FKL and gestational age, making FKL a valuable parameter for estimating gestational age in the third trimester. Its positive correlation with other biometric measurements (BPD, HC, AC, and FL) improves the accuracy of gestational dating during this stage of pregnancy. 

Source: Kalliyil F J, Narayanan S K, Rajan A P, Nair L R, Shenoy H T, Ramakrishnan, Tajunnisa M, Pregnancy dating: Determining gestational age through fetal kidney length-what do we observe?. Indian J Obstet Gynecol Res. 2024;11(4):548-552.