Abstract Aim: The purpose of this study was to determine the GA by using sonographic measurement of the (HL) and to confirm that if it is reliable in estimation of GA and comparing with that (FL) in second and third trimesters in normal fetuses. Methods: This was a descriptive cross-sectional study, consisted of normal pregnant women with singleton fetus during the second trimester and aim to evaluate the reliability of HL and FL in assessing the gestational age. This study included 175 normal pregnant women with singleton fetus, in their second trimester, with known LMP and healthy fetus. This study was conducted at the Ultrasound Department in Rajarajeswari medical college and hospital, in the period from January 2022- January 2023. Results: In the present study, there were 45 cases in 20 gestational week followed by 29 cases in 21 gestational week. There were 37 cases with age of 21 years followed by 28 cases with age of 20 years. 3 cases were with the age of 29 years. The minimum humerus length was 11 mm at 13 weeks and maximum was 38 mm at 24 weeks. The mean sonographic humerus length at 13 weeks was 7.1 – 10.3mm and at 24 weeks of gestation is 38.6 – 40.5mm. The minimum humerus length was 10 mm at 13 weeks and maximum was 38 mm at 24 weeks. The mean sonographic humerus length at 13 weeks was 7.6 - 10.3 mm and at 24 weeks of gestation is 41.4 – 43.5 mm. There was two-fold increase in humerus length from 13 weeks to 24 weeks. It demonstrates a linear relationship between foetal humerus length and gestational age. There were 37 cases with age of 21 years followed by 28 cases with age of 20 years. 3 cases were with the age of 29 years. Conclusion: The present study concluded that both femoral and humeral lengths were similar and reliable to estimate the GA. There was strong positive correlation between HL and gestational age done by (LMP). The HL is a basic of fetal biometry in determination of the GA and could be used in combines with FL to detect fetal bone abnormalities.