 News
7th April 2008
One in four
prem babies could get autismPremature babies could have as much
as a one in four risk of developing autism. The much higher rate offers
one explanation for the increase in children diagnosed with autism in recent years,
as early births have become more common. One in 100 Britons - around half
a million - are estimated to be autistic. Just 20 years ago, scientists
estimated that fewer than one in 1,000 people had the condition. But over
the same period, there has been a rise in the number of babies born prematurely
and surviving into adulthood. This is attributed to a combination of medical
advances and a trend for more older women, for whom premature babies are more
likely, to give birth. Almost one in eight babies are born prematurely
every year, according to baby charity Bliss. That equates to 76,000 babies
in the UK. The Canadian study involved children who were born between seven
and 14 weeks prematurely and weighed 3.3lb (1.5kg) or less at birth. A
behavioural test performed at around 21 months of age found suspected autism in
23 of the 91 children. The study also found that the risk of autism was
greatest among those children who were the smallest at birth. Experts say
babies born early may suffer mentally because their brain is still forming. Previous
studies have linked premature birth and low birth weight with developmental problems,
including autism. But the Canadian study is the first to attempt to quantify
the risk of autism. The danger was greatest among those children who were
the smallest at birth, and those born to mothers who suffered a prenatal infection
or bleeding, said Catherine Limperopoulos, lead researcher of the team from McGill
University in Montreal. "Early autistic behaviours seem to be an under-recognised
feature of very low birth-weight infants," she said. "Ongoing follow-up
is needed to understand if this initial positive screen is transient or persistent."
The toddlers who tested as being at high risk for autism were also more
likely to be male, and their mother was more likely to have experienced haemorrhaging
during labour and delivery. Autism can have relatively mild symptoms or
can severely disable a child by interfering with speech and behaviour. Higher
rates in recent years have been attributed to various causes, including improved
diagnoses. Other studies have found genetic and environmental links to
the condition. But now there is a growing belief that premature births may also
be a factor. The increasing number of mothers who delay giving birth until
their forties has been linked in studies to a serious increase in the number of
underweight babies. Most low birth-weight babies are born prematurely -
that is, born before 37 weeks' gestation. Britain has the second worst rate for
low birth weights in western Europe - second only to Greece. The number
of over-45s giving birth has doubled in a decade to 1,117 in 2005. Women
over 40 have an 8.5 per cent risk of giving birth to underweight babies, compared
with 6 per cent for those in their thirties. Other studies have shown that
premature birth and low birth weight babies are more prone to a low IQ, poor cognitive
functioning and learning disabilities. They are also more likely to exhibit
behavioural problems at school. On top of this, medical advances mean more
premature babies are surviving. Latest figures show that 39 per cent of babies
born at 24 weeks live - well up on previous years. The Canadian study was
published in the journal Pediatrics. Where to next?
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