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Objectives To determine the recurrence risk of a free trisomy 21 pregnancy. Methods Data from the National Down Syndrome Cytogenetic Register (NDSCR), which contains information on nearly all cases of Down syndrome between 1989 and 2001 in England and Wales were used. Among 11 281 women with a Down syndrome pregnancy who had had at least one previous pregnancy there were 95 women who had had a previous Down syndrome pregnancy. Results Women who have had a previous Down syndrome pregnancy have a constant absolute excess risk above their maternal age-related risk of having a subsequent affected pregnancy. This absolute excess risk is determined by the age at which the affected pregnancy occurred and is higher for younger than for older women. For example, after a Down syndrome pregnancy at age 20, this excess is 0.62% (95% CI: 0.24 to 1.15%) at early second trimester, and, after one at age 40, it is 0.04% (95% CI: 0.01 to 0.07%). Conclusion More precise risk estimates by single year of maternal age for use in genetic counselling are provided, but they need validation from other studies before they are incorporated in the risk estimation routines used in Down syndrome screening programmes. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objectives To determine the risk of a Down syndrome (DS) live birth for women 45 years of age and over. Methods A meta-analysis of data from five published articles, 13 EUROCAT congenital anomaly population registers and two unpublished sources. Results Information was available on the number of DS live births occurring amongst 13 745 live births to women 45 years of age and over. Information was also available on DS pregnancies diagnosed prenatally that were subsequently terminated. These pregnancies were adjusted for expected fetal loss to estimate the number of live births that would have occurred in the absence of prenatal diagnoses, when a total of 471 DS live births were estimated to have occurred. The risk of a DS birth did not increase for women 45 years of age and over. The average risk was 34 per 1000 births (95% CI: 31-37). Conclusion The risk of a DS live birth for women 45 years of age and over is considerably lower than has often been previously assumed. The most likely explanation is that women of this age are more likely to miscarry DS pregnancies than younger mothers. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study describes the cytological and epidemiological findings in 985 trisomy 13 and 2512 trisomy 18 compared with 10,255 trisomy 21 diagnoses between 2004 and 2009 included in the National Down Syndrome Cytogenetic Register of England and Wales. The frequency of occurrence, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Ninety-seven, 98%, and 92% were free karyotypes for trisomy 21, 18, and 13, respectively; 3% of 21, 1% of 18, and 8% of trisomy 13 were translocations; and under 1% of trisomies 21 and 18 were double or triple aneuploids. Overall 1% of each trisomy had mosaicism, but 48% of the trisomy 21 double aneuploids, and 10% of trisomy 18 multiple aneuploids had mosaicism. The proportion of livebirths was 40% of trisomy 21, 11% of 18, and 13% of 13, respectively. Free trisomies 21 and 13 had an excess of males, and 18 had an excess of females, as did mosaic free trisomies 21 and 18. Mean maternal ages were 35.9 years in trisomy 21, 36.4 years in 18, and 34.6 years in 13. During the 6 years of data collection 1% of the mothers had recurrences, most recurrent trisomy 21 or 18 were identical translocations, but hetero-trisomic recurrences included 21 and 18, and 21 and 13. There are significant differences between the trisomic karyotypes and attributes, possibly related to their variable origins. Notable are the relative excess of trisomy 13 translocations, mosaicism in cases with multiple aneuploidy, and the types of homo- and hetero-recurrences., (Copyright © 2012 Wiley Periodicals, Inc.)

This study describes the characteristics of karyotypes leading to phenotypic Down syndrome (trisomy 21) in 29,256 cases diagnosed between 1989 and 2009 in England and Wales included in the National Down Syndrome Cytogenetic Register (NDSCR). The frequency of occurrence of the different karyotypes, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Nearly 97% of all cases were free trisomy 21; 2.9% contributory trisomy 21, 0.3% double or triple aneuploidies; 1% of all were mosaics. Mean maternal age of free trisomy 21 cases was 35 years, 54% were male, and 1% of mothers had recurrences. Free trisomy 21 mosaics had a lower mean maternal age (33 years), a lower proportion of males (39.5%), and 2.5% of mothers had recurrences. The majority of contributory translocations were Robertsonian or rea (21;21). Their mothers were younger, particularly those of Robertsonian translocations (28 years). Of the Robertsonian der (14;21) translocations of known parental origin, 54% were de novo, 41% maternal and 5% paternal and 15.8% of mothers of those of maternal origin had recurrences. Multiple aneuploidies have the highest proportion of males (67%), highest proportion of mosaics (40%), a mean maternal age of 37 years, and no mothers had a recurrence. The size of this national register allowed the frequency of occurrence of the rarer karyotypes of Down syndrome to be estimated and their epidemiology described., (Copyright © 2012 Wiley Periodicals, Inc.)