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Iran J Public Health. 2015 Jun;44(6):791-6.

Screening of Fetal Chromosome Aneuploidies in the First and Second Trimester of 125,170 Iranian Pregnant Women.

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Tehran Genetic Clinic, 22 Keshavaraz BLvd., Tehran, Iran.
Niloo Laboratory, Valiasr Street, Tehran, Iran.
Tehran Genetic Clinic, 22 Keshavaraz BLvd., Tehran, Iran ; School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ; Dept. of Basic Sciences, Iranian Academy of Medical Sciences, Tehran, Iran.



Aneuploidy is one of the main causes of congenital anomalies, mental and physical disabilities, in newborns. The aim of this study was to determine various chromosomal aneuploidies in the first and second trimester screening of pregnant women, in Iran.


A descriptive retrospective study was conducted on 125,170 pregnant women referred to a major referral medical diagnostic laboratory (Niloo Laboratory, Tehran) for prenatal screening tests (2010-2013). Patients were divided into 3 groups: first trimester screening (FTS), second trimester screening (STS), and combined screening groups. In positive and borderline cases, and amniocentesis and cytogenetic analysis were carried out.


Total prevalence of aneuploidy in 125,170 pregnant women was one in 491, (Detection Rate=82.7% for Down syndrome). The DR for DS in three groups was as follow: 87.5% for FTS (25783 women), 80.9% for STS (91345 women), and 94.7% for combined tests (8042 women). Total number of cases with Edward's syndrome was 18, Patau's syndrome six, Klinefelter syndrome six, triploidy three, and Cri-du-chat syndrome one.


The present study shows the frequency of aneuploidy in the first and second trimester screenings in a major medical laboratory in Tehran. The prevalence of aneuploidies grows with increased maternal age. The rate of aneuploidy in first trimester is higher than second.


Aneuploidy; Chromosomal aberration; First and second trimester screening; Iran; Prenatal diagnosis


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