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To display and compare the different published formulae that specify the association between maternal age and the risk of a Down syndrome live birth. Papers published since 1987 on the prevalence of Down syndrome live births in relation to maternal age were located using MEDLINE and the references given in other papers. The data series and the models fitted to them were plotted to obtain a visual idea of their similarities and differences. The observed and modelled age-specific rates for Down syndrome births were remarkably similar in all published series of data for women up to the age of 35, were reasonably similar for women aged 35 to 45, but differed for women older than 45. In practice, the overall small differences in age-related risk between the different studies did not materially affect the performance of antenatal screening for Down syndrome. If a choice is to be made, the analysis based on the National Down Syndrome Cytogenetic Register (NDSCR) has marginal advantages since it is based on the largest data set and the corresponding model fits the data well. More data is needed to clarify the pattern of risk with maternal age among women over 45 years of age. Copyright © 2003 John Wiley & Sons, Ltd.

Associations between environmental hazards and the occurrence of congenital anomalies may be detectable by seeking evidence of non-random occurrence of cases (clusters). There have been a number of anecdotal reports of occurrences of clusters of Down syndrome (DS).

With the object of preparing a cellulose ether containing diazotizable amino groups, seven different forms of cellulose, or cellulose derivatives, were treated with 10 different reagents under a variety of conditions. Reasons why only one reagent under one set of conditions gave a product with a substantial degree of substitution (0.35) and with satisfactory physical properties are presented. This resulting ether, the ω-(P-aminoacetophenone) ether of cellulose, was prepared by the reaction between ω-chloro-P-aminoacetophenone and ethanol-washed soda-cellulose (from wood pulp, cotton, paper, or rayon). It can be (a) diazotized and coupled with any of the usual reagents to yield cellulose-azo colors, (b) xanthated, before or after coupling, and spun as rayon filament; if uncoupled at this point it can be diazotized and coupled, (c) dyed directly with acid dyes, (d) rendered organo-soluble by nitration, and (e) carboxymethylated after coupling to yield colored, water-soluble derivatives. It is insoluble in the usual cellulose reagents, and is as stable to acid and alkaline hydrolysis as cellulose.

Objectives— To evaluate the completeness of notifications of Down's syndrome live births and terminations to the Office for National Statistics (ONS) using data from the National Down Syndrome Cytogenetic Register (NDSCR). To examine the agreement of observed birth prevalence of Down's syndrome with the expected birth prevalence derived from published maternal age specific rates.Methods— The number of live births (adjusted to allow for the estimated under-ascertainment) and the number of terminations due to fetal Down's syndrome from NDSCR were compared with those figures reported to the ONS. Subsequently, using the NDSCR figures, the live birth prevalence of Down's syndrome that would have occurred in the absence of antenatal diagnosis and selective termination was calculated in England and Wales in the years 1990–1993. These figures were compared with those derived by applying published age specific prevalences to the maternal age distribution in England and Wales.Results— It is estimated that only 48% and 46% respectively of Down's syndrome live births and terminations of pregnancy were notified to ONS between 1990 and 1993. The annual expected birth prevalences of Down's syndrome obtained by applying maternal age specific prevalences to the maternal age distribution were in close agreement with observed rates from NDSCR.Conclusions— There is considerable underreporting of Down's syndrome births and terminations to ONS. The NDSCR data are more complete and therefore the effects of screening should be monitored using data from this source, or using estimates derived from the age specific rates of Down's syndrome.