Very premature babies at higher risk for autism, say McGill researchers

Preliminary results suggest 25% of very low birth weight infants showed signs of autism, higher risk for boys than girls

Very premature infants with low birth weight are more likely to show early signs of autism, according to a study conducted by McGill University researchers, along with colleagues from Children's Hospital Boston, Brigham and Women's Hospital and Harvard Medical School. Their study was published in the journal Pediatrics on April 3, the first World Autism Day, and was widely publicized globally in conjunction with the event.

"Extremely premature infants are known to have a high prevalence of learning disabilities, attention and behavioural problems," said McGill's Dr. Catherine Limperopoulos, lead author of the study, which was conducted at the two Boston hospitals. "Our findings suggest that early screening tests for autistic features might be warranted in this population. Should these children test positive on autism screening tests, follow-up specific diagnostic testing for autistic spectrum disorders should be performed."

Autism is a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behaviour, all starting before a child is three years old. It is the world's fastest-growing developmental disorder, affecting one child in 150 worldwide.

The longitudinal study followed 91 preterm infants who weighed less than 1500 grams at birth. The infants underwent conventional MRI studies prior to discharge from the neonatal intensive care unit. Pertinent demographic, prenatal, intrapartum and short-term outcome data were then collected and follow-up assessments were performed on all of the infants at 22 months. The results of the study found that 25% of the children assessed tested positive on an autism screen test.

Risk factors associated with a greater likelihood for positive result for autism included maternal infection and acute intrapartum bleeding, the baby's illness severity score after birth, low birth weight and gestational age, prenatal infection and abnormal MRI studies. Boys generated higher positive screening for autism than girls, which corroborates previous studies reporting a significant association between autism spectrum disorders and the male gender.

While the findings are significant, the researchers emphasize that their results are preliminary, based on a relatively small sample, and rely on a screening test which identifies infants who should undergo definitive diagnostic autism tests but does not diagnose autism directly.

"This research was done in a selected high-risk population of very preterm infants and by no means are we suggesting all premature babies are at risk for autism," said Limperopoulos, of McGill's Departments of Neurology and Neurosurgery and Pediatrics and the School of Physical and Occupational Therapy. "It is still unclear whether these initial findings are transient or whether they will persist in these children as they grow older."