Developmental Medicine & Child Neurology: “Neurocognitive outcomes of individuals with a sex chromosome trisomy”

In this study we have hard evidence that prenatal screening is being used to identify and abort biologically diverse intersex fetuses. The same study admits that there is little or no evidence of any distress or impairment associated with sex chromosome variation.

Much of the paper and its conclusions resemble the eugenics movement’s interpretation of inferior racial and ethnic differences from around the turn of the last century.

It appears that any departure from a medically mediated and determined ‘norm’ suffices for a recommendation of pregnancy termination.

OII has many members with chromosomal variations, including XXY. We are deeply troubled by this practice.


We conducted a systematic review of the past five decades of published data on cognitive and behavioural outcomes of individuals with an extra sex chromosome. The data were obtained primarily through published articles, although authors were contacted for clarification where appropriate. The online Web of Knowledge database was used to identify English-language articles, using the search terms (XXX OR XXY OR XYY OR sex chromosome (trisomy OR anomaly OR abnormality OR aneuploidy) OR Klinefelter) AND (cognit* OR language OR behav* OR brain OR neuro*). The search was confined to articles in databases for genetics, neuroscience, behavioural science, and psychiatry. Further articles were traced through PubMed and from reference lists in identified papers.

Because letter combinations such as XXX are used with various meanings in other disciplines, the search criteria generated many irrelevant papers, but these were readily identified, leaving 702 papers with a focus on chromosome abnormalities. As shown in Fig. 1, we excluded articles describing animal studies, those dealing with conditions other than SCTs, and those with no cognitive or neurodevelopmental content, leaving a pool of 424 publications to evaluate.

Developmental Medicine & Child Neurology: Neurocognitive outcomes of individuals with a sex chromosome trisomy: XXX, XXY or XYY: a systematic review


The information collected so far on individuals with SCTs indicates that this is a vulnerable group at increased risk of educational failure and neurodevelopmental disorder. However, there is considerable variation in outcomes within each of the three groups reviewed here. Furthermore, the majority of children with SCTs will be able to live independently and form close relationships as adults. Nevertheless, these conclusions are based on a remarkably small evidence base. The limited data from unselected studies suggest varied outcomes, but considerable work needs to be done to chart and understand this variability, and to explain the risks and protective factors that may be associated with outcomes at the cognitive and neurological level.

Because of difficulties in recruiting participants, recent studies have tended to be focused on cases identified in childhood or adulthood via self-help groups or genetics clinics, and most of these have been restricted to Klinefelter syndrome. Although these studies may provide useful insights into neuropsychological profiles and brain correlates in individuals with an extra X chromosome, they can give a misleading picture of the typical outcome, as they will inevitably exclude individuals who are not giving cause for concern.


Neonatal screening is no longer feasible, but there is potential for studying larger groups of children identified on prenatal screening. Although such a sample is not totally unbiased – it is likely to contain a disproportionate number of older parents and will inevitably include only those parents who decided to continue the pregnancy – it could provide valuable information on typical outcomes for children with SCTs, without the bias that comes from selecting only those cases diagnosed because of childhood problems. A dilemma for such a study is that the child may not have been told about the trisomy. Nevertheless, one could use standardized methods of parental reporting, which have provided valuable information in some of the studies reviewed here and typically agree well with direct testing.

In addition to informing our understanding of brain–behaviour relationships in people with an extra sex chromosome, we urgently need more information about the impact of SCTs to guide clinicians as they advise parents receiving a prenatal diagnosis about possible future outcomes, and to set the scene for targeted intervention early in life, where appropriate.

More information

For a wider discussion on this issue please see:

Jo Proctor: Neo-eugenics and its war against human biological diversity

Michael Noble: Representations of Klinefelter Syndrome