Genetic counseling dilemmas: Down syndrome,paternal age,and recurrence risk after remarriage

The recent demonstration that about 20–30% of cases of Down syndrome are of paternal origin has again raised interest in the question of the possible contribution of paternal age independent of maternal age to a couple's risk of a Down syndrome live birth. In this paper the nature of the available evidence is critically reviewed, interpretations reconciling differences between studies that reached opposite conclusions are presented, and an approach to genetic counseling in the face of such apparent differences in the literature is discussed. It is not likely that data from ad hoc studies of parental origin of the extra chromosome will be sufficient to judge the existence or magnitude of paternal age-specific risk, and reliance must be made on statistical studies that searched for paternal age effects while controlling for maternal age. The literature is consistent with an apparent doubling of risk for paternal age 55 and over, but no effect at younger paternal ages. With regard to remarriage, it is suggested that if members of a couple with a 47, +21 child remarry it be assumed that the excess risk “travels” to that new couple which includes the parent in whom non-disjunction occurred in the previous marriage. If parental origin is not known, it is suggested that the risk be calculated on the assumption of a 20–30% likelihood that it was of paternal origin and a 70–80% likelihood that it was of maternal origin, and that the excess empiric risks be apportioned accordingly in the new marriages.     

The incidence of Down syndrome in northern Finland with special reference to maternal age

The incidence of live-born children with Down syndrome was found to be 1.73/1000 (1:578) in northern Finland over the years 1965 to 1979. Despite a marked reduction in the proportion of older mothers, no significant change in the incidence was observed. Instead, an age-specific rise in the incidence for mothers aged 25 to 29 years could be shown during the last five-year period in years 1975 to 1979.     

Recent trends in the prevalence of Down syndrome in Japan, 1980–1997

The aims of the present study were to determine recent trends in the prevalence of Down syndrome (DS) in Japan, and to determine whether recent changes in demographic and social habits and access to prenatal diagnosis have influenced the livebirth rates of DS. Livebirth statistics indicate that the birth rate in Japan has decreased for women in their 20s and has increased for those in their 30s and 40s. During an 18-year period between 1980 and 1997, 1,299 consecutive DS infants were born among a total of 2,232,694 births, a rate corresponding to approximately 10% of all births in Japan over the same period. The increasing risk of DS with advancing maternal age was confirmed. The overall prevalence was 5.82 DS births per 10,000 livebirths (8.3–9.7 per 10,000 after correction according to the estimated ascertainment ratio: 60–70%). The prevalence rate by year of child birth represents a statistically significant increase (P = 0.001). In conclusion, recent trends in the prevalence of DS in Japan from 1980 to 1997 failed to show a consistent tendency to decrease, probably because of the concomitant increase in pregnancy in advanced maternal age. Am. J. Med. Genet. 84:340–345, 1999. © 1999 Wiley-Liss, Inc.     

Taschenatlas der Genetik. Eberhard Passarge. Georg Thieme Verlag,Stuttgart, New York, 1994, 406 pp

The presence of Y chromosome sequences in Ullrich-Turner syndrome (UTS) patients has been suggested in previous work. Karyotype analysis estimated at about 60% of patients with a 45, X constitution and molecular analysis (Southern blot analysis with several Y chromosome probes and PCR of specific sequences) identified the presence of Y chromosome material in about 40% of 45, X patients. We have developed a very sensitive, PCR-based method to detect Y specific sequences in DNA from UTS patients. This protocol permits the detection of a single cell carrying a Y sequence among 105 Y-negative cells. We studied 18 UTS patients with 4 Y-specific sequences. In 11 patients we detected a positive amplification for at least one Y sequence. The existence of a simple and sensitive method for the detection of Y sequences has important implications for UTS patients, in view of the risk for some of the females carrying Y-chromosome material of developing gonadoblastoma and viriliza-tion. Additionally, some of the UTS associated phenotypes, such as renal anomalies, could be correlated with the presence of Y chromosome specific sequences. © 1995 Wiley-Liss, Inc.     

Major congenital malformations in Down syndrome

We studied major malformations in 5,581 infants with Down syndrome (DS) from three registers of congenital malformations. The prevalence at birth of 23 different malformations was compared with the program-specific rates for each malformation in non-DS infants. An about 300 times risk increase was seen for annular pancreas, cataracts and duodenal atresia and an about 100 times risk increase for megacolon and choanal atresia. Esophageal, anal and small bowel atresia, preaxial polydactyly, and omphalocele all showed risk increases between 10 and 30 times. Statistically significantly elevated risk ratios around 3–5 were seen for cleft palate, cleft lip/palate, and limb deficiencies. No increased risk was seen for neural tube defects, hydrocephaly, microtia, renal agenesis or severe dysgenesis, hypospadias or polydactyly other than preaxial. Oral clefts were more often present in DS in the Swedish material than in the other two materials. Cardiac defects were registered in 26% of all cases (varying between programs) but 28% of the cardiac defects were unspecified. DS infants born to women younger than 25 years had a significantly increased risk for megacolon and there was a trend of increasing risk for esophageal or anal atresia with maternal age. A decreased risk for cardiac defect in DS infants born to teenage mothers was found, quite pronounced for endocardial cushion defects and ventricular septum defects. There were no statistically significant differences in the sex distribution of specific malformations in infants with DS and in non-DS infants. © 1996 Wiley-Liss, Inc.     

Search for ethnic,geographic, and other factors in the epidemiology of Down syndrome in South America: Analysis of data from the ECLAMC project, 1967–1997

We have analyzed data on 3,157 cases of Down syndrome (DS) from nine South American countries in consecutive series of hospital live births over a 30‐year period, with particular emphasis on possible ethnic or geographic variations in maternal age‐adjusted incidence. The data constitute the largest series of DS cases assembled to date from an area lacking advanced health care systems. Absolute incidence rates were estimated from total hospital live births; relative rates were estimated from matched case‐control data using conditional logistic regression. Maternal age‐adjusted rates were closely similar to those reported elsewhere, and showed little or no dependency on other factors investigated, including paternal age, birth order, ancestral origin, country of birth, maternal educational level, maternal ABO and Rhesus blood groups, interval to and outcome of mother's previous pregnancy, and parental consanguinity. The absence of an effect of high birth order was particularly notable because of the relatively large number of grand multipara resulting from high fertility in this population. The study adds to a body of evidence suggesting that maternal age‐adjusted DS rates vary little across human populations, and are therefore unlikely to be greatly influenced by genetic or environmental factors that differ between them. An unusual finding was of a markedly lower sex ratio (98 males per 100 females) than has been reported in other DS samples. © 2001 Wiley‐Liss, Inc.     

Performance of prenatal screening by non-invasive cell-free fetal DNA testing for women with various indicationsCSCD

Objective: To assess the performance of non-invasive prenatal testing (NIPT) based on massive parallel sequencing. Methods: A total of 10 275 maternal blood samples were collected. Fetal chromosomal aneuploides were subjected to low coverage whole genome sequencing. Patients with high risks received further prenatal diagnosis. The outcome of all patients were followed up. Results: High-throughput sequencing detected 72 pregnancies with fetal autosomal chromosomal aneuploidy, including 57 cases of trisomy 21, 14 cases of trisomy 18, and 1 case of trisomy 13. The positive predictive value for trisomies 21 and 18 were 98.25% and 91.67%, respectively. Comparing its performance in intermediate or high risk pregnancies, advanced maternal age pregnancies and volunteering to test pregnancies, the positive predictive value were 100%, 95%, 90% and 50%, respectively. The follow up result was only 1 case of 21 trisomy false negative with high risk. For the 56 cases of trisomy 21, the high risk group accounted for 55%, advanced maternal age accounted for 29%, the intermediate risk referred to 14%, the volunteering to test group accounted for 2%. Conclusion: The performance of NIPT for trisomies 21, 18 and 13 was satisfactory. The method can be used for women with advanced gestational age. NIPT has offered an ideal secondary screening method for those with an intermediate or high risk, and can reduce the rate of birth defects. © 2018 West China University of Medical Sciences. All rights reserved.     

Age-specific incidences of chromosome abnormalities at the second trimester amniocentesis for Japanese mothers aged 35 and older: collaborative study of 5484 cases

The aim of this study was to calculate the expected incidences of chromosome abnormalities found at amniocentesis in Japanese women aged 35 and older. From four clinics in Japan, we gathered genetic amniocentesis data on 5484 pregnant women at risk only due to their advanced age, 35 years and older. We analyzed the data using the logistic regression model. Of the 5484 fetuses, 117 (2.1%) were diagnosed with a chromosome abnormality. The abnormal karyotypes included 42 cases of trisomy 21; 13 of trisomy 18; 7 of trisomy 13; 10 of 47,XXY; 4 of 47,XXX; 1 of 47,XYY; 27 with various structural aberrations; and 13 with various types of mosaicism. The incidences of trisomy 21, lethal autosomal aneuploidies (trisomy 18 and trisomy 13), and sex-chromosome abnormalities (XXY, XXX, XYY) increased with maternal age. Parameters of the regression equations with their standard errors were calculated and the expected incidences of chromosome abnormalities at each maternal age were derived. The expected incidences of chromosome abnormalities obtained in this study are the first data published for Japan and will be useful for the counseling of pregnant women. The incidence of trisomy 21 is not different from the rates published previously for Western countries. The incidences of chromosome abnormalities are not affected by race or by geographic factors. Received: July 23, 1997 / Accepted: December 1, 1997     

The relative risk for standard 21 trisomy has not increased in young mothers in Belgium, 1960–1978

In the present investigation we directly studied the constancy of the relative risks for standard 21 trisomy in Belgium during the period 1960-1978. The relative risk for standard 21 trisomy in different maternal age-groups, as compared to 20-24 years and 40-44 years remained remarkably constant during the period under investigation. The increasing percentage of children with standard 21 trisomy born to younger mothers does not result from an increased risk for mothers of this maternal age-group, but results from the general shift towards a younger maternal age at birth for the total population of births in Belgium.     

Maternal age and down syndrome: Age-specific incidence rates by single-year intervals

Maternal age-specific risks of giving birth to a child with the Down syndrome (DS) are given by single-year age intervals. Such data are of value for more precise genetic counseling and in cost-benefit analyses of prenatal diagnosis programs. The data were obtained by linking records of children with DS at the British Columbia Health Surveillance Registry (BCHSR) to the appropriate birth registrations to derive maternal ages. The data related to 519 affected children out of a total of 354,880 live births in British Columbia between 1961 and 1970. The results, which are based on a high level of ascertainment, are compared to those reported in the only other published study relating to risks by single-year maternal age groupings, where completeness of ascertainment was estimated to be only 38%.     

Determinants of parental decisions after the prenatal diagnosis of Down syndrome

We evaluated demographic factors and factors specific to the current pregnancy, and their relationship to the decision to continue or terminate a pregnancy after prenatal diagnosis of Down syndrome. All cases of Down syndrome (DS) managed at a tertiary care center from 1989–1997 were retrospectively analyzed with respect to maternal age, parity, gestational age, sonographic findings, insurance status, and race. Of 145 cases of trisomy 21, 19 (13.1%) of women chose continuation of pregnancy, while 126 (86.9%) chose termination. There were no differences between groups in parity, sonographic findings, insurance status, or race at the time of diagnosis. However, patients who chose termination were significantly older and earlier in gestation than those electing to continue their pregnancy. When Down syndrome is diagnosed prenatally, the choice of termination is related to maternal age and gestational age, but only gestational age is a significant independent predictor of pregnancy termination. Am. J. Med. Genet. 79:172–174, 1998. © 1998 Wiley-Liss, Inc.     

171例唐氏综合征患者的细胞遗传学分析

本文通过对171例唐氏综合征的细胞遗传学检查，进行外周血染色体核型分析，对导致染色体畸变的诱因进行了调查，在此基础上进行分析和讨论。再次证明染色体畸变是唐氏征的根本原因，而导致染色体畸变的诱因有母亲的年龄，环境等因素，它具有偶发性。我们必须加强孕妇的环境保护，加强唐氏征的预防和筛查工作。     

Cytogenetic,epidemiological and clinical profile of children with Down syndrome in Karnataka

Introduction

Down syndrome is one of the best recognized and the most common chromosomal aneuploidy with high life expectancy than other chromosomal aneuploidies. The clinical features are quite distinguishing and easily identifiable, but a karyotype analysis is always better to confirm the diagnosis. It is also needed for calculating the risk of recurrence and for genetic counseling. This study was done to analyze the clinical features, cytogenetic and epidemiological profile of Down syndrome children in Tumkur and Bangalore region of Karnataka.