Autism is a neurodevelopmental disorder that is characterised by problems with social interaction, verbal and non-verbal communication and restricted interests and behaviours.

However, experts noted that the increase in risk was slight, and they found no association between maternal smoking and more severe forms of autism.

What the findings suggest is that although autism spectrum disorders share many of the same symptoms, subtypes of the disorder likely have many different genetic and environmental causes that vary from person to person and by type of autism, explained study author Amy Kalkbrenner, an assistant professor in the University of Wisconsin-Milwaukee Zilber School of Public Health (USA).

“We know ‘autism spectrum disorders’ is an umbrella term. What we’re showing is the response to a environmental toxin may differ by the subtype of autism a child has,” Kalkbrenner said.

The study

Kalkbrenner and her colleagues examined data on maternal smoking from birth certificates of nearly 634 000 US children born in 1992, 1994, 1996 and 1998. That data was compared with information on 3315 children aged 8 and under diagnosed with an autism spectrum disorder from the US Centres for Disease Control and Prevention’s Autism and Developmental Disabilities Monitoring Network.

The researchers found that about 13% of the mothers smoked during pregnancy, and 11% of the mothers of kids with an autism spectrum disorder smoked during pregnancy.

According to the study, kids born to moms who smoked during pregnancy had about a 25% increased risk of having high-functioning autism, such as Asperger’s syndrome. However, the results did not reach statistical significance.

Underreported

The researchers noted that the data used in the study may underestimate the true prevalence of autism spectrum disorders among mothers who smoke because lower-income kids are less likely to be identified as having autism, and lower-income mothers are also more likely to smoke during pregnancy.

When researchers did another statistical analysis that took into account a suspected undercounting of kids with autism, the analysis did suggest a statistically significant association between smoking and high-functioning autism in offspring.

There are multiple reasons why tobacco might raise the risk of autism, Kalkbrenner noted. Tobacco can restrict oxygen flow to the baby, while the nicotine is known to interact with the nervous system and cross the placenta into the developing foetus. “There are many potential biological pathways for which tobacco can harm the developing baby,” she said.

Source: HealthDay News