Shahid Sadoughi University of Medical Sciences Journal of Integrated Maternal and Pediatric Care 2645-4068 5 2 2022 12 01 Positive Predictive Value of Screening Tests in the First and Second Trimester of Pregnancy in the Diagnosis of Trisomy 21, 18, and 13 Using Amniocentesis 74 82 308 10.18502/wjpn.v5i2.11994 EN Fatemeh Farzan The Ali-ibne-Abitaleb School of Medicine, Islamic. Azad University of Yazd, Yazd, Iran Ali Dadbinpour Genetic and Environmental Adventures Research Center, School of Abarkouh paramedicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Department of Medical Genetics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Sedigheh Ekraminasab Mother and Newborn Health Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Department of Hematology and Blood Banking, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Hossein Fallahzadeh Research Center of Prevention and Epidemiology of Non-Communicable Disease, Department of Biostatistics and Epidemiology, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mahta Mazaheri Department of Medical Genetics, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Mother and Newborn Health Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Stem Cell Biology Research Center, Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Journal Article 2022 12 28 <strong>Background:</strong> The aim of this study is to analyze the positive predictive value (PPV) of trisomies 21, 18 and 13 at first and second trimester using amniocentesis for clinical practice.<br /><strong>Methods:</strong> : This is a descriptive cross-sectional study in which data were extracted from a cohort project of mother and infant conducted between March 2016 and February 2021 among 3110 pregnant women in Yazd city.<br /><strong>Results: </strong>Out of 3110 pregnant women, 84 mothers were at high risk in the screening tests of the first and second trimesters of pregnancy and therefore were candidates for amniocentesis. None of them were detected by the positive amniocentesis method. The mean age of mothers was 33.2 years. The causes of amniocentesis included old age (45.9%), positive results of Down syndrome screening (23%), high NT ultrasound (4.9%), and pathological results of anomaly scan sonography (3.8%).<br /><strong>Conclusion:</strong> In this study, the PPV was zero and the number of false positives in screening tests was 84 (100%). This may be because our population was normal and had no history of genetic abnormalities or other special conditions. https://wjpn.ssu.ac.ir/article_308_9e9c12ca2c0d4fb9db6e05e5908c4f81.pdf