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OBJECTIVES To investigate a reported cluster of Down's syndrome in offspring of former pupils of a girls' school in Ireland, to establish the prevalence of Down's syndrome among live births in the area around the school, and to review the literature on the possible causes of reported clusters of Down's syndrome. METHODS Questionnaire survey of obstetric and personal histories of women who had attended the girls' school at Dundalk, County Louth, Republic of Ireland, at some time during 1956–7, and also of women who had attended another, nearby, girls' school during the same period. Comparison of observed numbers of cases of Down's syndrome identified by these surveys with maternal age adjusted expected numbers for the reported live births. Laboratory tests were conducted to verify and characterise the cases of Down's syndrome constituting the cluster. Retrospective collection and collation of data on Down's syndrome occurring among live births, and the compilation of maternal age specific incidences, in County Louth and in Newry and Mourne District in neighbouring Northern Ireland, during 1961–80. These rates were compared with reference rates and rates for other areas of Ireland. RESULTS Six children with Down's syndrome were confirmed among 387 reported live births to women who had been pupils at the girls' school in Dundalk during 1956–7, compared with 0.69 expected (nominal p<10-4). Five of the affected births were to mothers under 30 years of age, against 0.15 expected (nominal p<10-6), although only four of these mothers were attending the school at any one time. The origin of the non-disjunction was found to be maternal first meiotic in four children, mitotic after fertilisation in another (with the youngest mother), and in the remaining one could not be determined. The marked excess of Down's syndrome in births to young mothers did not extend to offspring of former pupils of the other Dundalk girls' school surveyed, or to live births in County Louth generally or in adjacent Newry and Mourne District. CONCLUSION A striking, highly localised, excess of Down's syndrome in births to young mothers who had attended a girls' school in Dundalk during 1956–57 has been confirmed. However, not all of the mothers of the affected children attended the school concurrently and the origin of non-disjunction in one child was an error occurring after conception. Some exposure essentially confined to girls attending the school at this time is a possible, although unlikely, explanation, but a review of potential risk factors does not suggest what this could be. Previous suggestions that an influenza epidemic or contamination from the Windscale nuclear reactor fire might be implicated, both of which occurred in October 1957, can be effectively dismissed because three of the women with affected offspring had left the school by then and had moved away from Dundalk, and Down's syndrome in the child of another mother originated in an error after fertilisation. Owing to the retrospective nature of the investigation and the characteristics of the cases, chance is the most likely explanation for the cluster.

Satellite imagery is a useful tool to assess large-scale (>103 km2) geological patterns. Satellite imagery of north central Ireland shows cross-cut and overprinted subglacial bedform patterns. Bedform lineations, supported by sedimentary evidence, are used to reconstruct four ice-flow stages (named A-D) during the termination of the last (Devensian) glaciation (22 000-13 000 radiocarbon (14C) years BP). Flow stage A relates to southwesterly flow of Scottish ice across eastern Ireland. Flow stage B, during the last glacial maximum (c. 25 000-22 000 14C years BP), records southeasterly ice-flow from dispersal centres in northern parts of Ireland. Transverse subglacial ridges (Rogen moraines) formed during stage B are the largest area of this ridge type in western Europe. Flow stage C records erosional headcutting in the Rogen moraine field and sediment streamlining (drumlinization) by ice streams drawn into the Irish Sea Basin. This flow stage is constrained by AMS radiocarbon dates from marine microfaunas to around 14 500 14C years BP. Flow stage D records drumlinization from an inland centre in the Lough Neagh Basin. Overall bedform patterns can be used to reconstruct ice mass history and evaluate controls on ice activity, including millennial-scale changes in amphi-North Atlantic climate. Field evidence of bedform relationships also casts doubt on current concepts of drumlinization and the role of pervasive sediment deformation in glacial systems.

In 1976 Dr Patricia Sheehan, a Dublin doctor, was talking to a mother who had a Down syndrome child. Down syndrome, a disorder in which there are three chromosomes number 21 instead of the usual two, is also called trisomy 21. It causes changes in appearance which gave the disorder its old name, ‘mongolism’, and usually causes mental retardation. The mother told Dr Sheehan that there were other girls who had attended her school, St Louis, in Dundalk, Co. Louth, in 1956/57 who also had Down syndrome babies and that the mothers were young when the babies were born. Patricia