It is the first time that a clear link has been made between babies who grow to above average size at birth and risk of Autism Spectrum Disorder and follows from a study of more than 40,000 child health records in Sweden.
The research, led by The University of Manchester, also confirms earlier research which reported that premature and poorly grown, low weight babies appear more susceptible to the condition.
Autism affects how individuals interact with the world and with other people and there is no known cure. One child in 100 has the condition in the UK according to NHS figures. Researchers believe it has origins in both genetic and environmental causes.
Professor Kathryn Abel, from the University's Centre for Women's Mental Health and Institute of Brain, Behaviour and Mental Health, led the research published in The American Journal of Psychiatry.
Professor Abel said: "The processes that leads to ASD probably begin during fetal life; signs of the disorder can occur as early as three years of age. Fetal growth is influenced by genetic and non-genetic factors. A detailed understanding of how fetal growth is controlled and the ways in which it is associated with ASD are therefore important if we are to advance the search for cures.
"To our knowledge, this is the first large prospective population-based study to describe the association between the degree of deviance in fetal growth from the normal average in a population of children and risk of ASD with and without intellectual disability.
"We have shown for the first time categorically that abnormal fetal growth in both directions increases risk of autism spectrum disorder."
Researchers looked at data from the Stockholm Youth Cohort in Sweden, where early ultrasound dating provides detailed weights of the baby's progression in pregnancy. Infants and children then also take part in structured clinical assessments of their social, motor, language and cognitive abilities.
|Contact: Alison Barbuti|
University of Manchester