Women who smoke during pregnancy are more likely to have children with high-functioning autism, a new study suggests.

"It has long been known that autism is an umbrella term for a wide range of disorders that impair social and communication skills," lead researcher Professor Amy Kalkbrenner from the University of Wisconsin-Milwaukee's Joseph J. Zilber School of Public Health said in a statement released on Thursday.

“What we are seeing is that some disorders on the autism spectrum, more than others, may be influenced by a factor such as whether a mother smokes during pregnancy,” she added.

Kalkbrenner and her research team analyzed a population-based study that compared smoking data from birth certificates of 633,989 children, born in 1992, 1994, 1996 and 1998 from 11 different states.

The findings reveal that 13 percent of the mothers of children included in the study had smoked during pregnancy and that 11 percent of the 3,315 children that were identified as having an autism spectrum disorder at age eight, had mothers who had smoked during pregnancy.

Researchers also found that these children were more likely to have less severe high-functioning autism, like Asperger’s Disorder.

"The study doesn't say for certain that smoking is a risk factor for autism," Kalkbrenner said. "But it does say that if there is an association, it's between smoking and certain types of autism."

The study was published on Wednesday online by the journal Environmental Health Perspectives.

Each time a pregnant woman smokes a cigarette, toxic chemicals get into her bloodstream and then into the baby’s source of oxygen and nutrients, which are essential for a baby’s healthy development.

Smoking while pregnant increases a woman’s chance of having a miscarriage, stillbirth, premature birth or having a baby with low birth rate. Babies born to mothers who smoked during pregnancy are also more likely to die from Sudden Infant Death Syndrome and have a higher risk of being born with birth defects like a cleft palate, and developing asthma and ear infections.

According to the U.S. Centers for Disease Control and Prevention’s 2008 Pregnancy Risk Assessment and Monitoring System, based on data from 29 states, 13 percent of women reported smoking during the last three months of pregnancy.

The CDC reported last month that about one in 88 children in the United States have an autism spectrum disorder, the highest estimate to date, making environmental studies like the latest “even more timely,” Kalkbrenner said.

She adds that autism involves a wide-ranging spectrum of conditions that are triggered by a combination of genetics and environment that is so complex, no one study can explain all the causes of autism.

"The goal of this work is to help provide a piece of the puzzle. And in this we were successful," she concluded.

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