Written By: IJCP Editorial Team

Published On: 24 Jul, 2025 5:21 PM | Updated On: 27 Jul, 2025 10:58 AM

A New Marker for Late Pregnancy Dating: Fetal Kidney Length

Accurate assessment of gestational age is critical for optimal obstetric management, particularly in guiding decisions related to pregnancy progression and the risk of preterm labor. Ultrasound-based fetal biometric measurements remain a reliable tool for this purpose.

This study aimed to evaluate the utility of fetal kidney length (FKL) as a parameter for estimating gestational age during the third trimester and to compare its accuracy with traditional biometric indices and the gestational age calculated from the last menstrual period (LMP).

A prospective study was conducted over nine months (September 2016 to May 2017), involving 200 pregnant women in their third trimester. Fetal kidney length was measured via ultrasound, along with standard biometric parameters including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL).

The findings revealed a strong positive correlation between fetal kidney length (in millimetres) and gestational age (in weeks), with a Pearson’s correlation coefficient of 0.87—indicating a statistically significant relationship.

In conclusion, fetal kidney length demonstrates a clear linear relationship with gestational age and can serve as a valuable adjunct for dating pregnancies in the third trimester. Its strong correlation with other biometric markers (BPD, HC, AC, and FL) enhances the precision of gestational age estimation during this period.

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.