13 Correspondence Dr. Mahesh Gautam Department of Radiology, Nobel Medical College Teaching Hospital, Biratnagar, Nepal Email: mahes.gautam07@gmail.c om, Phone: +977-9852084876 ORCID: https://orcid.org/0000- 0003-3978-3770 Received: 29 Dec 2021 Accepted: 1 June 2022 Citation: Gautam M, Khanal B, Dhakal A, Pathak MR, Tiwari S. Ultrasound measurement of fetal kidney length in the second and third trimester of pregnancy and its correlation with gestational age. Nep J Obstet Gynecol. 2022;17(35):13-19. DOI: https://doi.org/10.3126/njo g. v17i2.52369 Ultrasound measurement of fetal kidney length in the second and third trimester of pregnancy and its correlation with gestational age Mahesh Gautam 1 , Bipin Khanal 2 , Amita Dhakal 3 , Manish Raj Pathak 4 , Sagar Tiwari 5 1 Department of Radiology, Nobel Medical College Teaching Hospital, Biratnagar, Nepal; 2 Department of Radiology, Rapti Academy of Health Science, Dang, Nepal, 3 Department of Obstetrics and Gynecology, Nobel Medical College Teaching Hospital, Biratnagar, Nepal; 4 Department of Radiology, Birat Medical College and Teaching Hospital, Biratnagar, Nepal; 5 Medical epidemiologist, Bharatpur Central Hospital, Chitwan, Nepal ABSTRACT Aims: To measure the fetal kidney length in the second and third trimesters of pregnancy and correlate it with the gestational age and other routine fetal parameters. Methods: This prospective cross-sectional study includes 250 pregnant women presented in the Nobel Medical College for ultrasound examination from the period of July 2021 to June 2022. Gestational age was estimated based on the last menstrual date and ultrasonogram. Routine fetal parameters and mean fetal kidney length were measured. The correlation between gestational age, fetal kidney length, and routine fetal parameters was studied. Results: The mean gestational age according to ultrasound and last menstrual period were 35.5 ± 3.4 weeks and 35.2 ± 3.2weeks respectively. The mean fetal kidney length was 36.8 ± 4.02mm. There was a very strong positive correlation between gestational age and fetal kidney length (r=0.921, p =0.001). Compared to the routine fetal parameters, adding fetal kidney length improved the effectiveness in predicting gestational age. (R 2 =0.918 vs. R 2 =0.936) Conclusion: Fetal kidney length can be added to the other standard parameters to improve the prediction of gestational age. Keywords: fetal ultrasonography, gestational age, kidney length INTRODUCTION Accurate estimation of gestational age (GA) is crucial for selecting the most appropriate mode of delivery and the GA also influences the choice of management and the result. Different parameters are used for the estimation of GA in various stages of pregnancy. The last menstrual period (LMP) and mean sac diameter is more reliable in the first trimester. 1 As the pregnancy progresses biparietal dia- Gautam M et al. Fetal kidney length and gestational age. NJOG. Jul-Dec. 2022;17(35):13-19 Original