BACKGROUND; Accurate assessment of gestational age is first and foremost for the obstetrician to date the pregnancy as early as possible during antenatal examination for the better management of pregnancy. The traditional fetal biometric parameters, such as biparietal diameter (BPD), head circumference (HC), abdominal circumference(AC) and femur length (FL), become increasingly unreliable for accurate gestational age estimation, with advancing pregnancy, especially in 3rd trimester. This study was conducted to assess the role of fetal kidney length (KL) as an alternate parameter to assess gestational age in 2nd and 3rd trimesters and to compare its accuracy with other biometric parameters. Aim; To assess the relationship between sonographic gestational age and fetal KL between 16 and 40 weeks of gestation and to compare its accuracy with other biometric parameters. Materials and methods; Prospective, cross–sectional, single operator study of 500 antenatal cases between 16 to 40 weeks of gestation where in bipolar measurement of both kidneys, mean were taken along with other biometric parameters. The 500 cases were grouped in to five groups ie16 to 20 weeks n= 93, 21 to26weeks n=91, 26 to 30 weeks n=96, 31 to35 weeks n=135 > 36 weeks n=85. Statistical analysis is done using, Stat14, The r and p value of each group, for each biophysical parameter were highly significant and are less the r value of o.4726 and p value of 0.001 respectively. Results; A strong statistical correlation was found between sonographic gestational age and fetal KL. Monograms and growth curves were constructed to correlate gestational age with fetal KL.