Review of epidemiological factors (other than maternal age) that determine the prevalence of common autosomal trisomies

Cuckle, Howard; Benn, Peter

doi:10.1002/pd.5822

Cited by 12 publications

(12 citation statements)

References 103 publications

(211 reference statements)

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“…What is the consequence of having a low‐level residual abnormal cell population that may be substantially confined to specific tissues and undetected in those tissues routinely analyzed when a chromosome abnormality is suspected? Possibilities include recurrence for common autosomal trisomies, 93 recurrent pregnancy loss with identical chromosome imbalances, premature ovarian failure, 94 and cancer 95 . The term “occult mosaicism” has been proposed to describe the situation where mosaicism is hidden but suspected on the basis of clinical findings 96 .…”

Section: Relevance Of Mosaicism To Nipt Using Cfdnamentioning

confidence: 99%

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

et al. 2021

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The diagnosis of chromosomal mosaicism in the preimplantation and prenatal stage is fraught with uncertainty and multiple factors need to be considered in order to gauge the likely impact. The clinical effects of chromosomal mosaicism are directly linked to the type of the imbalance (size, gene content, and copy number), the timing of the initial event leading to mosaicism during embryogenesis/fetal development, the distribution of the abnormal cells throughout the various tissues within the body as well as the ratio of normal/abnormal cells within each of those tissues. Additional factors such as assay noise and culture artifacts also have an impact on the significance and management of mosaic cases. Genetic counseling is an important part of educating patients about the likelihood of having a liveborn with a chromosome abnormality and these risks differ according to the time of ascertainment and the tissue where the mosaic cells were initially discovered. Each situation needs to be assessed on a case‐by‐case basis and counseled accordingly. This review will discuss the clinical impact of finding mosaicism through: embryo biopsy, chorionic villus sampling, amniocentesis, and noninvasive prenatal testing using cell‐free DNA.

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Section: Relevance Of Mosaicism To Nipt Using Cfdnamentioning

confidence: 99%

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

et al. 2021

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“…The proportion of common autosomal trisomies births attributable to maternal age depends on the age distribution. It has been estimated that for England and Wales, in 2017, the proportion was about three‐quarters 54 . The identification of causal factors in the remaining cases is difficult to establish because of strong confounding by age and gestation.…”

Section: Origins Of Aneuploidymentioning

confidence: 99%

Maternal age in the epidemiology of common autosomal trisomies

Cuckle

Morris

2020

Prenatal Diagnosis

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The birth prevalence rate of each common autosomal trisomy generally increases with advancing maternal age and there is a substantial fetal loss rate between late first trimester and term. The literature is reviewed in order to provide the best estimates of these rates, taking account where possible of biases due to prenatal diagnosis and selective termination of pregnancy. There is an almost exponential increase in Down syndrome birth prevalence between ages 15 and 45 but at older ages the curve flattens. There is no evidence of the claimed relatively high birth prevalence at extremely low ages. Gestation‐specific intra‐uterine fetal loss rates are estimated by follow‐up of women declining termination of pregnancy after prenatal diagnosis, comparison of observed rates with those expected from birth prevalence and comparison of age‐specific curves developed for prenatal diagnosis and birth. Down syndrome fetal loss rates reduce with gestation and increase with maternal age. Edwards and Patau syndrome birth prevalence is approximately 1/8 and 1/13 that of Down syndrome overall, although the ratio differs according to maternal age, particularly for Patau syndrome where it reduces steadily from 1/9 to 1/19. Fetal loss rates are higher for Edwards and Patau syndromes than for Down syndrome.

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“…Rates of other chromosome abnormalities in twin pregnancies have not been established from direct observations and estimates are based on their proportionate relationship to trisomy 21 in singleton pregnancies. 5 Conventional combined serum and ultrasound-based screening for aneuploidy has been shown to have a lower detection rate and/or higher false-positive rate than that achievable in singletons. 6 Maternal serum markers are unable to distinguish between monozygotic and dizygotic twins and since most affected pregnancies are F I G U R E 1 Heterozygosity plots for single nucleotide polymorphisms (SNPs) in euploid twin pregnancies.…”

Section: Use Of Cf-dna To Screen For Aneuploidymentioning

confidence: 99%

Non‐invasive prenatal testing in the management of twin pregnancies

Benn

Rebarber

2021

Prenatal Diagnosis

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Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta-analyses show that non-invasive prenatal testing (NIPT) through analysis of cell-free DNA (cf-DNA) is superior to serum and ultrasound-based tests.The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT.Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf-DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf-DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies. Key PointsWhat's already known about this topic? � In singleton pregnancies, non-invasive prenatal testing (NIPT) for fetal aneuploidy is more effective than conventional serum and ultrasound-based screening tests.� NIPT is more complex in dizygotic twin pregnancies due to the presence of two fetal genotypes.� Overall fetal fraction is higher in twin pregnancies but the individual contribution for each fetus is lower. What does this study add?� A review of cell-free DNA testing in twin pregnancies.� Individual fetal fractions in dizygotic twin pregnancies can be measured.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Review of epidemiological factors (other than maternal age) that determine the prevalence of common autosomal trisomies

Cited by 12 publications

References 103 publications

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

Maternal age in the epidemiology of common autosomal trisomies

Non‐invasive prenatal testing in the management of twin pregnancies

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