I am not sure why, but the figure most often quoted for the number of babies with Down syndrome born each year recently in the UK is 750. I am guessing this figure is drawn on data published the National Down Syndrome Cytogentic Register. However, this is does not cover the whole of the UK – only England and Wales.
England and Wales is fortunate to have a registry recording the births of babies with Down syndrome. It has reported live births, prenatal diagnoses and pregnancy outcomes since 1989 with a high degree of accuracy. In fact, it offers probably one of the most useful datasets available anywhere in the world.
Rather irritatingly, the work of NDSCR has recently been transferred the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS) and the Congenital Anomaly Register and Information Service (CARIS) for Wales. The move around means no data for 2014 or 2015 has been published for England. I am told it will be next year before this appears. CARIS only appears to be reporting total cases, which is unhelpful. Hopefully, the NCARDRS and CARIS will pool their data to continue to publish the England and Wales data series.
Scotland reports live births back to 1991, though apparently not prenatal diagnoses and pregnancy outcomes. Northern Ireland does not seem to publish data on live births of babies with Down syndrome.
Drawing on these data sources, we can compile a total for UK live births going back to 1991:
As Northern Ireland does not seem to publish a count of live births of babies with Down syndrome, I have estimated them by taking published data on all live births broken down by age of mother and multiplying these by the formula expressing the maternal-age-related chance of having a baby with Down syndrome (to get the expected number of ‘natural’ live births in the absence of selective terminations). I have then reduced this number at the same rate as ‘natural’ live births have been reduced by terminations in each year in England and Wales. To estimate births in 2014 and 2015 for England and Wales, and for 2012-15 for Scotland I have again calculated the expected ‘natural’ live births and reduced by the recent average reduction rates in each area. (Of course, the reduction rates may have risen in the past few years with the private availability of NIPT, but we do not have the data yet to see this.)
Given these assumptions, we can calculate that the average annual live births of babies with Down syndrome in the United Kingdom over the past 5 years is 847.
|Year||England and Wales||Scotland||Northern Ireland||UK||5-year UK average|
As ever, I must acknowledge helpful discussions about the data with my colleague Gert de Graaf. As soon as we can get the most recent data I hope we will publish a larger historical births and populations dataset. However, any errors are all mine!