A study led by Simon Baron-Cohen (Department of Psychiatry) has found that children, who later develop autism, have elevated levels of steroid hormones in the womb. The finding may help explain why autism is more common in males than females. However, the researchers caution it should not be used to screen for the condition.

The team of researchers, utilized approximately 19,500 amniotic fluid samples from individuals born between 1993 and 1999. Amniotic fluid surrounds the baby in the womb during pregnancy and is collected when some women choose to have an amniocentesis around 15-16 weeks of pregnancy. This coincides with a critical period for early brain development and sexual differentiation, and thus allows scientists access into this important window in fetal development. The researchers identified amniotic fluid samples from 128 males later diagnosed with an autism spectrum condition and matched these up with information from a central register of all psychiatric diagnoses.

Professor Baron-Cohen said: “This is one of the earliest non-genetic biomarkers that has been identified in children who go on to develop autism. We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail, and more autistic traits. Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism. Because some of these hormones are produced in much higher quantities in males than in females, this may help us explain why autism is more common in males.”