Babies whose growth is at either extreme in the womb, either very small
or very large, are at greater risk of developing autism, a new study has
revealed.
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 confirmed 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. 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, who led the research 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.
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.
The cohort contained records of
589,114 children aged 0-17 in Sweden between 2001 and 2007. Certain
child data was removed, including children too young to have a diagnosis
for ASD, adopted children and non Swedish or Stockholm County
residents, children not born in Sweden and twins.
From the
remaining available data, researchers found 4,283 young people with
autism and 36,588 who did not have the condition and who acted as the
control.
The study found that bigger babies who were born
weighing over 4.5kg (or 9lb 14) showed a higher incidence of autism, as
did smaller infants who were born weighing less than 2.5kg (5.5lb).
A
baby who had poor fetal growth would therefore have a 63 percent
greater risk of developing autism compared to normally grown babies. A
baby who was large at birth would have a 60 percent greater risk. This
effect was independent of whether or not the baby was born pre or post
term.
Professor Abel added: "We think that this increase in risk
associated with extreme abnormal growth of the fetus shows that
something is going wrong during development, possibly with the function
of the placenta.
"Anything which encourages abnormalities of development and growth is
likely to also affect development of the baby`s brain. Risk appeared
particularly high in those babies where they were growing poorly and
continued in utero until after 40 weeks. This may be because these
infants were exposed the longest to unhealthy conditions within the mother`s womb," she stated.The research was published in The American Journal of Psychiatry this month.
Source : Zee News Health , 3rd May 2013
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