UK scientists have identified a link between levels of testosterone exposure in the womb and the appearance of 'autistic traits' in childhood. The research, carried out at the University of Cambridge, found that higher prenatal levels of the hormone were linked to an increased incidence of poor verbal and social skills in children aged 6-10. The findings, published in the British Journal of Psychology, triggered a media debate on the ethics of prenatal screening for autism last week, although this was not the focus of the study.
The results were based on a study of 235 children whose mothers underwent routine amniocentesis - a pregnancy testing technique in which a small amount of amniotic fluid (the liquid that surrounds and protects the fetus) is removed for analysis. These samples, collected in the Cambridge region between 1996 and 2001, did not include any from pregnancies later found to be affected by a genetic or other medical problem.
The scientists measured levels of testosterone present in the amniotic fluid, to investigate the hypothesis that prenatal exposure to the hormone may be responsible for some of the key differences between male and female brains. In particular, some scientists think that autism disorders may represent an 'extreme form' of the typical male brain. None of the children in the study had autism, but the team found that higher prenatal testosterone levels were statistically more likely to predict the appearance of autistic traits, as measured using standard questionnaires.
The researchers acknowledge that larger studies are now needed to confirm the association, to see if it applies to children diagnosed with autism, and to find out if the relationship is causal - for example, it could just be that the same genetic variations that affect testosterone levels may also affect the development of autistic traits. It is also likely to be just one risk factor of many different genetic and environmental differences that affect the development of the disorder.
However, team leader Professor Simon Baron-Cohen believes that issues surrounding prenatal testing for autism should be discussed before such tests ever become available. He told the Guardian newspaper: 'We should start debating this. There is a test for Down's syndrome and that is legal and parents exercise their right to choose termination, but autism is often linked with talent. It is a different kind of condition'.