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Genetic Counseling in Assisted Reproductive Technology
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
There are three viable autosomal trisomies associated with recognized syndromes: trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). Embryos reported to have trisomy 21 have an increased risk of miscarriage. When detected prenatally, pregnancies with trisomy 21 have only about a 24% chance of developing to term. Individuals with Down syndrome have varying degrees of cognitive impairment and birth defects, including characteristically dysmorphic facial features and heart defects. Down syndrome affects approximately 1 in 800 individuals in the general population.
Second-trimester screening for fetal abnormalities
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Jolene C. Muscat, Anthony M. Vintzileos
Trisomy 13 is the third most common of the autosomal trisomies to result in a live-born neonate. Prevalence of this disorder ranges between 1 in 5000 to 1 in 20,000 and it is characterized by multiple severe anomalies resulting in neonatal death (81). Severe craniofacial and midline defects are more common and severe in this trisomy when compared with the abnormalities seen in trisomy 18 or 21 fetuses. As with trisomy 18 fetuses, second-trimester sonographic examination can show many of the anomalies characteristic of trisomy 13. In one series of 28 fetuses with trisomy 13, major structural malformations were seen in 23 cases (82.1%) and minor anomalies were detected in 16 cases (57.1%) (82). Among major anomalies, the most common (64.3%) were central nervous system (ventriculomegaly, holprosencephaly, posterior fossa cysts) and facial (midline clefts, microphthalmos, protrusio bulbi, hypertelorism). Cardiovascular anomalies were the next most common abnormality detected (53.6%) followed by renal anomalies (42.9%) and polydactyly (7.1%). Ultrasound markers for fetal aneuploidy were also detected (57.1%), but almost always in association with a major structural defect (87.5%).
Miscarriage
Published in Botros Rizk, A. Mostafa Borahay, Abdel Maguid Ramzy, Clinical Diagnosis and Management of Gynecologic Emergencies, 2020
Erich T. Wyckoff, Hadeer Usama Ebrahem Metwally
On occasion, it is useful to further classify miscarriages as early or late, according to whether they occur before or after the 12th week of gestation [3]. Pregnancy loss prior to the 12th week is referred to as early pregnancy loss. The majority of these miscarriages are caused by chromosome abnormalities that make it impossible for the fetus to develop normally [4]. Fetal chromosomal abnormalities cause 70% of first-trimester miscarriages and 30% of second-trimester miscarriages [1]. More specifically, autosomal trisomies are the most common type of chromosomal anomalies [1]. They result from nondisjunction during meiosis. Maternal age is a risk factor for increasing incidence of trisomy pregnancies and hence increased rates of miscarriage. Among women who know they are pregnant, about 10% to 25% will have a miscarriage. In women older than age 40 years, the sporadic miscarriage rate approaches 50% [5].
The predictive value of noninvasive prenatal screening for copy number variations: a cohort study and a systematic meta-analysis
Published in Expert Review of Molecular Diagnostics, 2023
Li Wen, Yanzhen Zhang, Jiye Gao, Wensheng Hu
Noninvasive prenatal screening (NIPS) is one of the prenatal screening strategies that fully utilizes cell-free DNA (cfDNA) in the blood of pregnant women to identify fetal chromosomal anomalies. Since NIPS was first introduced into clinical practice in October 2011, numerous studies have reported on the testing for common aneuploidies (trisomy 21/18/13) and proved high screening accuracy [1–3]. However, these aneuploidies only account for a proportion of chromosomal abnormalities in prenatal diagnosis [4,5]. The rapid development of massive parallel sequencing has enabled the detection of other types of chromosomal abnormalities, such as sex chromosome aneuploidies (SCAs) [6], rare autosomal trisomies (RATs) [7] and subchromosomal copy number variations (CNVs) [8]. The clinical performance of cfDNA screening for these genetic abnormalities is not as well reported yet as common trisomies. The lack of data regarding the screening performance for CNVs complicates pretest and posttest counseling, especially since pregnant women tend to be extremely anxious after receiving a screen-positive result.
Noninvasive prenatal screening in southeast China: clinical application and accuracy evaluation
Published in Expert Review of Molecular Diagnostics, 2022
Li Wen, Jiye Gao, Leilei Huang, Dongmei Li, Guansheng Zhong
Noninvasive prenatal screening (NIPS) has been widely adopted in clinical practice to detect fetal chromosomal aneuploidy with its high sensitivity and specificity [1–4]. It, taking advantage of cell-free DNA (cfDNA) in maternal plasma [5] and the massive parallel sequencing technologies [6,7], is capable of reporting common autosomal trisomies [Trisomy 21 (T21), Trisomy 18 (T18), and Trisomy 13 (T13)], as well as the sex chromosome aneuploidy (SCA) [8,9]. The most frequently occurred SCAs are Turner syndrome (45,X), Triple X syndrome (47,XXX), Klinefelter syndrome (47,XXY), and Jacob syndrome (47,XYY), with the incidence ranging from 1/850 to 1/500 for female and male fetuses, respectively [10,11]. Meanwhile, compared with other lethal chromosome abnormality, T21, T18, T13, and SCAs with intellectual disability or sexual organ dysplasia were exist approximately in 0.3% of live births [12]. This makes prenatal testing for common trisomies and SCAs an attractive option in pregnant women. As a matter of fact, in China, NIPS has been recommended as a routine screening strategy because of its easier operation, less invasive risk, and more accurate results, in contrast with other prenatal screening technologies [13]. However, parts of pregnant women still get the false positive results by NIPS, despite it is reported to be highly reliable in assessing common autosomal trisomies. False positive rate of SCAs is relatively much higher, leading unnecessary anxiety in pregnancy and making clinical counseling after test more complex.
First trimester prenatal detection of mosaic trisomy 8
Published in Journal of Obstetrics and Gynaecology, 2021
Li Wan, Dan Yang, Bi-Qiu Xu, Li Zhen, Yan-Dong Yang, Dong-Zhi Li
A 37-year-old G2P1 woman was referred to our centre for prenatal diagnosis at 11 weeks of gestation. She had a healthy 6-year-old girl. The mother had a routine first-trimester scan at another clinic with her nuchal translucency (NT) measured 1.0 mm. She opted for cell-free DNA-based NIPT instead of a direct invasive procedure after a detailed genetic counselling. The NIPT result was available at 12 weeks of gestation, and reported a low risk for common aneuploidies, but a high risk for trisomy 8 (Z-score 9.44) (Figure 1(A)). Considering the very low positive predictive values (PPVs) of rare autosomal trisomies (RATs) in NIPT, follow-up ultrasound examinations were recommended. A first-trimester anatomic scan revealed cleft palate in the foetus with a crown rump length of 5.3 mm and NT thickness of 1.8 mm (Figure 1(B)). No other obvious anomalies were noted. After another genetic counselling, the woman opted for genetic testing by amniocentesis. At 16 weeks of gestation, a repeat scan confirmed the cleft lip and palate with no other notable findings. Amniocentesis was offered at 16 weeks, and a microarray analysis using CytoScan 750 K Array (Affymetrix Inc., Santa Clara, CA) revealed a male karyotype with an estimated 40% mosaicism for trisomy 8. The cell culture, however, showed a chromosome formula of 46,XY in 50 metaphases examined.