Abstract

Introduction: Based on the international and standard definitions confirmed by WHO and FIGO, post-term pregnancy s applied to cases in which gestational age extends for 42 weeks (294 days) and more. Methods: In this review article, the databases Medline, Cochrane, Science Direct, and Google Scholar were thoroughly searched to identify the efficacy of Ultrasound in determining the gestational age in the first trimester and decreasing the rate of post-term pregnancy In this review, the papers published until early January 2017 that were conducted to study the efficacy of Ultrasound in determining the gestational age in the first trimester and decreasing the rate of post-term pregnancy were selected. Findings: Exact and precise determination of gestational age is a very important factor in maintaining the health of the pregnant mother and the new born. Knowledge of the gestational age has a significant effect on genetic studies and the sampling, chorionic pelvic and amniocentesis, biochemical screening tests, the method of delivery and fetal development. Discussion and conclusion: With the advancement of technology, determining the most clinically appropriate and cost-effective method for estimating the gestational age has become more and more important. Nowadays, despite added care costs, ultrasound is preferred to other available and inexpensive methods, such as measuring the height of the uterus, to estimate the gestational age. © 2017, Pharmainfo Publications. All rights reserved.