Pregnancy dating: Determining gestational age through fetal kidney length-what do we observe?

Accurate gestational age is crucial for obstetric care, pregnancy management, and preterm labor decisions. Ultrasound, based on fetal biometric parameters, is a reliable method for this purpose. This study aims to estimate gestational age in the third trimester using ultrasonographic methods, focusing on fetal kidney length. Gestational age is estimated in the third trimester by measuring fetal kidney length and comparing it with gestational age derived from other biometric parameters (bi-parietal diameter, head circumference, abdominal circumference, and femur length) and the last menstrual period (LMP). A nine-month prospective study was conducted Kozhikode, Kerala, from September 2016 to May 2017. The study involved 200 women in their third trimester of pregnancy, utilizing third-trimester ultrasound to measure and document kidney length along with other biometric parameters (BPD, HC, AC, and FL). Subsequently, the collected data was reviewed and analyzed. : The study revealed a strong positive correlation between fetal kidney lengths (FKL) measured in millimeters and gestational age in weeks during the third trimester. The correlation was significant, with a Pearson's correlation coefficient of 0.87 (p < 0.001). Additionally, FKL exhibited positive correlations with other variables, including abdominal circumference (r = 0.832), head circumference (r = 0.845), bi-parietal diameter (r = 0.838), and femur length (r = 0.837). These findings demonstrated a strong Pearson’s correlation (r= 0.87-0.96, P <0.05) for all the biometric parameters including FKL. A linear relationship exists between fetal kidney length (FKL) and gestational age, allowing FKL to serve as an effective parameter for estimating gestational age during the third trimester. Given its positive correlation with other fetal biometric parameters such as bi-parietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL), incorporating FKL alongside these measurements enhances the accuracy of gestational dating in the third trimester. This combination of parameters improves the prediction of gestational age during this stage of pregnancy.