Balkan Journal of Medical Genetics

POLYPLOIDY PHENOMENON AS A CAUSE OF EARLY MISCARRIAGES IN ABORTION MATERIALS
Yildirim ME, Karakus S, Kurtulgan HK, Ozer L, Celik SB
*Corresponding Author: Malik Ejder Yildirim, Associate Professor. Department of Medical Genetics, Faculty of Medicine, Sivas Cumhuriyet University, 58104 Sivas, Turkey. Phone: 03462581085, Email: nemalik2002@gmail.com
page: 5

INTRODUCTION

A miscarriage is defined as the loss of pregnancy before 20 weeks of estimated gestational age [1]. The first definitive ultrasound evidence of intrauterine pregnancy is the observation of the yolk sac, which should appear by 6 weeks after the last menstrual period [2]. About 10 to 20 percent of known pregnancies result in miscarriage. A miscarriage may be an isolated status or it may occur repeatedly and it is generally accepted that 1 out of 5-6 pregnancies results in miscarriage. However, recurrent miscarriages occur in only 1-2% of couples [3]. Most miscarriages occur in the first trimester, especially between 8th and 12th weeks [4]. The etiology of spontaneous abortion is often unclear and, in this context, it may be multifactorial [5]. There may be various causes of abortion, including anatomical, genetic, immunologic, endocrine, and thrombophilic problems [6]. Since a significant number of pregnancies are lost before implantation, they are not clinically recognized [7]. About 50% of first trimester abortions are caused by chromosomal abnormalities such as aneuploidy and can be determined by conventional cytogenetic analysis. It is claimed that 86% of these abnormalities are numerical, 6% are structural abnormalities and 8% of them result from other genetic mechanisms [8]. Chromosomal variations found in material obtained from chorionic villus sampling are considered to be the chromosome structure of the fetus in the majority of cases [9]. Embryonic aneuploidy, which increases notably with advanced maternal age, constitutes a large part of spontaneous abortion [10]. Recurrent aneuploidy/ polyploidy is an event largely related to maternal age but in rare cases, couples may experience recurrent aneuploidy/polyploidy as a result of gonadal mosaicism or another maternal age-independent state [11]. On the other hand, paternal age is also a risk factor that may increase the possibility of spontaneous abortion, independent of certain conditions, such as socio-demographics and maternal age [12]. Trisomy is the presence of an extra copy of a chromosome in the cell nucleus and it is one of the most common chromosomal abnormalities in miscarriages. In a study conducted with FISH method in early miscarriages, 37.3% of the cases were found to have aneuploidy and 7% have polyploidy. Moreover, it was reported that paternal age may be associated with the risk of fetal aneuploidy in this research [13]. Triploidy is a chromosomal abnormality in which a cell has three copies of each chromosome and this accounts for 1% of conceptions. Most of the affected fetuses are usually lost during the first trimester [14]. Tetraploidy is defined as the presence of four haploid sets of chromosomes in the cell nucleus. Complete tetraploidy is usually fatal, and very few live births with this condition have been reported so far [15]. Besides conventional cytogenetic analysis, more detailed techniques can be used to analyze miscarriage specimens including fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH) [16]. In this study, we aimed to examine the karyotype of abortion materials and to detect possible numerical and structural chromosome abnormalities from polyploidy and aneuploidies to translocations.

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