Genetic Counseling and Prenatal Diagnosis of Triploidy During the Second Trimester of Pregnancy

Abstract

Introduction:Triploidy is a lethal chromosomal numeric abnormality, characterized on extra haploid set of chromosomes. It occurs in 2 to 3% of conceptuses and accounts for approximately 20% of chromosomally abnormal first-trimester miscarriages. As such, triploidy is estimated to occur in 1 of 3,500 pregnancies at 12 weeks’, 1 in 30,000 at 16 weeks’, and 1 in 250,000 at 20 weeks’ gestation.Case report:We present a case of second-trimester triploidy diagnosed prenataly at our center. 28-years-old gravida with a first spontaneous pregnancy had early gestational hypertension. Ultrasound examination in 146/7 weeks’ gestation revealed asymmetric intrauterine growth retardation. We recommended biochemical maternal serum screening during second trimester of pregnancy (AFP, HCG, uE3). Result of biochemical screening was indication for cytogenetic analysis from amniotic fluid cells and we recommended early amniocentesis in 156/7 weeks’ gestation. Result showed abnormal karyotype of the fetus (69,XXX triploidy), and DNA analysis confirmed Type-2 Diginy. Parents decided to terminate this pregnancy, and it was done at 22 weeks’ gestation.Conclusion:We emphasize the importance of non-invasive prenatal exminationes-biochemical serum screening during second trimester of pregnancy, and ultrasound examinations in prenatal screening of syndroma Down and other chromosomal abnormalities.

Polyploidy Phenomenon as a Cause of Early Miscarriages in Abortion Materials

“…Polyploidy cases can be found at a high rate in spontaneous abortions, and they are expected to be lethal with multiple congenital defects. Triploidy is a numerical chromosomal aberration characterized by the presence of an extra haploid chromosome set and may occur in approximately 17% of spontaneous abortions in first trimester [ 27 ]. A third chromosome set in this condition may originate either from the mother or the father at the time of fertilization.…”

Sequential application of copy number variation sequencing and quantitative fluorescence polymerase chain reaction in genetic analysis of miscarriage and stillbirth

“…Therefore, triploidy is a non‐negligible etiological cause of early pregnancy losses, and genetic testing methods must be able to detect triploidy. Theoretically, the sex chromosomes in triploid individuals of maternal origin should be in 50% of the cases XXX and 50% XXY, and in those of paternal origin, 25% XXX, 50% XXY, and 25% XYY (Kolarski et al, 2017 ). Therefore, the ratios of XXX, XXY, and XYY among triploidies were expected as 37.5%, 50%, and 12.5%, respectively.…”

Prenatal diagnosis of syndromic alobar holoprosencephaly associated with digynic triploidy fetus

“…The prevalence of fetal triploidy is estimate to one per 100 of human conceptuses. Because the most of fetuses with triploidy are spontaneously aborted in the first trimester of pregnancy, at the beginning of the second trimester of pregnancy, the prevalence of triploidy is about one in each 5000 gestations [ 19 , 20 , 21 , 22 ].…”

“…There are diverse mechanisms that may produce triploidy: diandric triploidy, when the supplementary haploid chromosome set has paternal origin, or digynic triploidy, when the supplementary haploid chromosome set has maternal origin [ 19 ]. Digynic triploidies origin result from fertilization of a primary oocyte, a diploid oocyte or retention of a polar body [ 22 ]. The substrate of human triploidy is disputed [ 23 , 24 ].…”