There has been comment about recent coverage on the BBC and elsewhere of changing attitudes towards Down's Syndrome. My colleague Rob Ketteridge, editor of the documentaries unit in Audio and Music Factual, explains.
- By Rob Ketteridge
- On Monday 24 November the Radio 4 documentary "Born With Down's" and BBC News reported that more babies are being born with Down's Syndrome than at any time since prenatal screening began in 1989. In 1989 there were 717 Down's Syndrome births. This figure then fell to a low point of 572 in 2001, since when there has been a steady increase to 749 in 2006 - the last year for which figures are available. Since 2001 the proportion has risen ahead of the overall birth rate.
- So far so good and accurate. But do the headline statistics support the idea that more parents are choosing to continue with pregnancies after Down's Syndrome has been diagnosed or when it is a high risk? And if so, is there any evidence that a reason for this could be that social attitudes towards Down's Syndrome are changing?
- Since the documentary was broadcast these questions have become a matter of fierce debate, with some of the medical experts and statisticians as well as some journalists challenging these hypotheses. One issue they have raised is that there has been an increase in the number of older mothers with a higher risk factor for Down's Syndrome during this period. They argue that the rising trend is therefore predictable and without prenatal screening it would be significantly higher. They also state that from 1989 to 2006 the proportion of women choosing to terminate a pregnancy following prenatal diagnosis of Down's Syndrome has remained constant at around 92%.
- To shed more light on this, we need to look at the data in more detail. Bear with me because things are about to get more complex.
- The figures are published annually by the National Down Syndrome Cytogenetic Register run by Joan Morris who is Professor of Medical Statistics at the Wolfson Institute of Preventive Medicine in London. Follow this link [pdf] and look at Table 7 on Page 8 of the latest report for 2006. The table shows that in 1989 there were 1033 diagnoses of Down's Syndrome in total, of which only 30% approximately (318) were prenatal. There were 717 live births and 290 terminations that year. In 2006 there were 1877 diagnoses, of which approximately 60% or 1132 were prenatal, leading to 749 live births and 767 terminations.
- So: in 1989 there were 318 prenatal diagnoses and 290 terminations; in 2006 there were 1132 prenatal diagnoses and 767 terminations. On the face of it, the proportion for those choosing to terminate after a prenatal diagnosis in 2006 doesn't look anything like the 92% figure.
- But - and it is an important but - the 2006 figures also reveal that in that year there were 293 cases of "Unknown Outcome" - a figure that has also been rising over the years. If a high proportion of these were in fact terminations then the 92% figure starts to look accurate.
- Last week I contacted Professor Morris to ask about this. She said: "To obtain the true proportion of women who decide to terminate their pregnancy we had to analyse a subset of the data from cytogenetic laboratories for whom we had excellent follow-up (in other words areas of the country in which we had extremely few unknown outcomes). In these laboratories we found that 92% of prenatal diagnoses were terminated." A footnote to the published tables also states that: "A large proportion of the missing outcomes are from one single large private cytogenetic laboratory in London, which analyses samples from women throughout the South East of England."
- So: there is little evidence here, according to Professor Morris, for a shift in social attitudes leading more parents to continue with a pregnancy after Down's Syndrome has been diagnosed prenatally. Some have argued that the consistency of the 92% figure over this period isn't in itself very surprising: the diagnostic tests (such as amniocentesis) carry a small risk of miscarriage and the argument is that most parents who go ahead with them are likely to be decided on termination already if a positive diagnosis is received.
- However none of this tells us much about the still large number of cases where a conclusive prenatal diagnosis isn't made. In some cases parents might have refused diagnostic testing because of the miscarriage risk or because they had decided to continue with the pregnancy whatever the outcome might be.
- What do we know about the views of parents in this last category? There has so far been little evidence. Surprised by the rising numbers, the Down's Syndrome Association conducted a survey of some of its members to coincide with the programme. In many cases religious reasons were given for continuing with a pregnancy when Down's Syndrome had been diagnosed or was a high risk. But, as we reported, a significant number also cited changing social attitudes towards people born with Down's Syndrome.
- Such evidence is interesting but inconclusive. What is more certain is that the original documentary and other reports could have included more information about the complexity of the data underneath the headline figures - as necessary qualification and context - and more fully represented the debate about how to interpret it.
- Better understanding - not just of the data and other evidence, but also of Down's Syndrome itself and social attitudes towards it for which we are all responsible - seems to be clearly needed. Primarily, though, the documentary focussed movingly, and from more than one point of view, on parents who have Down's Syndrome babies and it engaged with their experiences.
I would just add that one of the claims made by Ben Goldacre in his Bad Science blog and Guardian column is that when Professor Morris issued her clarifications after the story was initially covered in newspapers and online, "everybody ignored them, nobody has clarified". That's not true - our website's health pages were updated as soon as we had spoken to her.