Open Journal of Medical Imaging, 2014, 4, 126-132 Published Online September 2014 in SciRes. http://www.scirp.org/journal/ojmi http://dx.doi.org/10.4236/ojmi.2014.43018 How to cite this paper: Falatah, H.A., Awad, I.A., Abbas, H.Y., Khafaji, M.A., Alsafi, K.G.H. and Jastaniah, S.D. (2014) Accura- cy of Ultrasound to Determine Gestational Age in Third Trimester. Open Journal of Medical Imaging, 4, 126-132. http://dx.doi.org/10.4236/ojmi.2014.43018 Accuracy of Ultrasound to Determine Gestational Age in Third Trimester Hebah A. Falatah 1 , Ibrahim A. Awad 1 , Hanan Y. Abbas 1 , Maway A. Khafaji 2 , Khalid G. H. Alsafi 2 , Saddig D. Jastaniah 1* 1 Department of Diagnostic Radiology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, KSA 2 Department of Radiology, School of Medicine, King Abdulaziz University, Jeddah, KSA Email: * sjastaniah@kau.edu.sa Received 27 June 2014; revised 28 July 2014; accepted 28 August 2014 Copyright © 2014 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract Rapid and accurate determination of gestational age (GA) may be vital to the appropriate care of the critically ill pregnant patient and improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. Ultrasound scans are consi- dered to be the most cost-effective, accurate and safe methods for measurement of various fetal parts in pregnant women. The aim of this research is to explore the accuracy of ultrasound in de- termining gestational age of fetus in third trimesters. Data collected for all pregnant women re- ferred to the Maternity & Children’s Hospital in Jeddah. Only women with single live fetus were in- cluded in this study. Women who participated in the study were selected on following criteria: Regular menstrual cycles, known date of last menstrual period and previous live normal neo- nates in multipara. All scans were performed by a single ultrasonologist on one ultrasound ma- chine. From collected data, it was found that out of 53 (100%) patients, 44 (84.62%) pregnant woman have different gestational age from US and last menstrual period (LMP). From this study we can conclude that the main method to follow fetus growth in third trimester not biparietal di- ameter (BPD) measurement only. The BPD in third trimester is not reliable and be useless when the patient pass 30 weeks and the BPD has to be side with other measurements when we take it in later trimesters to emphasize the normal growth of fetus and avoid wrong measurement of ultra- sound. Keywords Ultrasonography, GA, BPD, Third Trimester * Corresponding author.