WEDNESDAY, April 2 (HealthDay News) -- Two new studies shed additional light on two different aspects of autism: One tried to pinpoint a risk factor for development of the disorder, while the other looked at the financial toll that having an autistic child takes on a family.

Both studies were expected to be published in the April issue of Pediatrics and were released early in honor of World Autism Day on April 2.

The first looked for early autistic behaviors, though not specifically for a diagnosis of autism, in premature infants who were born at a very low birth weight -- about 3.3 pounds -- and found that several factors associated with these early births were linked to a positive result on an autism screening test.

"The bottom line is that there appears to be a high prevalence of positive screening for autism in survivors of extreme preterm birth and ongoing follow-up is needed to understand if this initial positive screen is transient or persistent," said study author Catherine Limperopoulos, the Canada Research Chair in Brain and Development and an assistant professor in the department of Neurology and Neurosurgery at McGill University in Montreal.

"There is a suggestion [from this study] that preterm infants may be at risk for developing autism, but this is really a preliminary finding that needs to be replicated in a large, prospective study," said Andy Shih, vice president of scientific affairs for Autism Speaks, in New York City.

Limperopoulos and her colleagues studied 91 babies who weighed less than 3 pounds at birth. MRIs were done on these infants around the time they were born. The researchers collected information on the child's health and demographic information, as well as information on their prenatal environment.

At around 22 months, the researchers conducted an autism screening test, called the Modified Checklist for Autism in Toddlers or M-CHAT, as well as other behavior tests. The M-CHAT test is only used to screen children who might have an elevated risk of autism; it is not a definitive diagnostic tool.

Twenty-five percent of these toddlers tested positive on the M-CHAT, suggesting that they had an increased risk of developing autism. Factors that were significantly associated with a positive M-CHAT screen included lower birth weight, lower gestational age, being male, having an abnormal MRI, being ill when delivered, an infection in the mother before birth, or the mother experienced hemorrhaging during labor and delivery.

Limperopoulos said this study wasn't designed to determine causality, but that some type of prenatal or perinatal insult might increase the likelihood of autism.

"I think it's a great study," said Dr. Sara Hamel, a developmental pediatrician in the Child Development Unit at Children's Hospital of Pittsburgh. "A group of infants born preterm and at a low birth weight underwent screening for autism features, and about 25 percent screened positive. That doesn't mean they have it, but that they're at risk. This study really lends weight to the idea that if you screen children around 18 months old, you'll find a number of kids who test positive and need further diagnostic assessment."

The second study assessed some of the financial impact that having a child with autism can have on a family's finances, and found that when a child has autism, the family earns an average of $6,200 less each year, or about 14 percent.

"We think parents are making different decisions about labor participation," said study author Guillermo Montes, a senior researcher at Children's Institute in Rochester, in New York. "In some cases, one parent stays home, another may turn down a promotion or might take a job that doesn't require as much travel," which ultimately reduces the family's earning power.

And, he added, the income lost is just part of the equation.

"This is just the income they don't make," he noted. "The literature has shown that these families have additional health-care expenses, [and] pay for special diets and other therapies not covered by their health insurance," Montes said.

More information

To learn more about autism, visit the Autism Society of America.