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A study released Wednesday in conjunction with World Autism Day suggests that premature babies are at greater risk of being diagnosed with autism.

The study looked at 91 babies with an average gestation time of 26 weeks. Researchers in Montreal and Boston performed standard development tests on the babies between the ages of 18 and 24 months.

Of the 91 babies tested, 25 per cent had a positive result on an autism screening test. Researchers say they don't know what proportion of these high risk children will go on to develop autism and are currently performing more confirmatory tests. Results will be released in 6-9 months.

Babies were at higher risk of scoring positive on the autism screening test if they had been more ill at birth, if they were male, or had a lower birth weight or gestational age at birth and if the mother had a prenatal infection.

"The results suggest the more premature the infant and the greater the complications at birth, the greater the likelihood they will follow up with a positive score for autism," the study's lead author, Catherine Limperopoulos of McGill University, told CTV's Avis Favaro.

"Even more troubling, among preemies who had bleeding in a part of the brain known as the cerebellum, 100% - all of them - developed signs of autism."

The study, entitled "Positive Screening for Autism in Ex-Preterm Infants: Prevalence in Risk Factors," was published Wednesday in the journal Pediatrics.

Limperopoulos said that the results do not mean that premature birth causes autism. But it may just put premature babies at higher risk of developing the disorder.

"Testing positive on an autism screening test does not mean that you are autistic," said Limperopoulos. "It means that you likely warrant testing. And what I mean by testing is standardized, definitive diagnostic tests."

Advances in treatment options for premature babies means more are surviving - and are then susceptible to related complications. Limperopoulos said that her objective with the study was to perform a screening test for autistic features on kids with a very low birth weight. The babies in this study were all born at less than 1,500 grams.

The test, known as the Modified Checklist for Autism Todders (M-CHAT), asked parents to complete a questionnaire about their child's behavior, evaluating actions such as if the child responds to his or her name, overreacts to a noise or being touched and imitates his or her parents. An interview with the parents and observation of the child's behavior were also part of testing.

"My message to parents and to primary health-care providers is that early autistic features seem to be under-recognized in survivors of extreme pre-term birth," said Limperopoulos. "And this may warrant regular systematic first-line screening in all survivors in order to identify children who may be testing positive initially and then should be followed by definitive autistic diagnostic testing."

Dr. Wendy Roberts of the Hospital for Sick Children in Toronto said that this is a new avenue of study for researchers. Investigations into the long-term effects of being born prematurely had previously focused on motor and language development and learning disabilities.

"I think it points to the fact that premature children are a very high risk group," said Roberts. "They need to be followed for learning problems, motor problems and yes, they are at a very higher risk of having some autistic features."

Autism is a disorder that has no known cause or cure and encompasses a wide variety of symptoms related to the inability to communicate and engaging in destructive behaviors. There are therapies that can dramatically improve symptoms, but they need to begin early in a child's life.

Michael DeWit, whose son Nicholas was born 11 weeks early, noticed the signs of unusual behaviour early. Nicholas was later diagnosed with autism. He started receiving therapy after he was 3 and a half.

"The best advice for any parent of any child and certainly in the case of a premature child is watch for signs even more closely," said DeWit. "Watch for signs of delays, watch for signs for things that are a little unusual."

According to the Canadian Autism Society, parents can look for specific characteristics in their child that do not confirm an autism diagnosis, but could mean that they should talk to their child's doctor. These include:

• Lack of imaginative and social play.
• Difficulty making friends within own age group.
• Inability to initiate or sustain a conversation.
• Stereotyped, repetitive, or unusual use of language.
• Restricted and/or overly-intense interests.
• Overly dependent on specific routines or rituals.
• Preoccupied with parts of objects.

Abstract

OBJECTIVE. The survival of very low birth weight infants has increased markedly in recent years. Unfortunately, the prevalence of significant and lifelong motor, cognitive, and behavioral dysfunction has remained a major problem confronting these children. The objective of this study was to perform screening tests for early autistic features in children with a history of very low birth weight and to identify risk factors associated with a positive screening result.

METHODS. We studied 91 ex-preterm infants 1500 g at birth. Infants underwent conventional MRI studies at preterm and/or term-adjusted age. We collected pertinent demographic, prenatal, intrapartum, acute postnatal, and short-term outcome data for all infants. Follow-up assessments were performed at a mean age of 21.9 � 4.7 months, using the Modified Checklist for Autism in Toddlers, the Vineland Adaptive Behavior Scale, and the Child Behavior Checklist.

RESULTS. Twenty-six percent of ex-preterm infants had a positive result on the autism screening tool. Abnormal scores correlated highly with internalizing behavioral problems on the Child Behavior Checklist and socialization and communication deficits on the Vineland Scales. Lower birth weight, gestational age, male gender, chorioamnionitis, acute intrapartum hemorrhage, illness severity on admission, and abnormal MRI studies were significantly associated with an abnormal autism screening score.

CONCLUSIONS. Early autistic behaviors seem to be an underrecognized feature of very low birth weight infants. The results from this study suggest that early screening for signs of autism may be warranted in this high-risk population followed by definitive autism testing in those with positive screening results.

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