If a girl's maternal grandmother smoked during pregnancy, the girl is 67 per cent more likely to display certain traits linked to autism, such as poor social communication skills and repetitive behaviours, says a study.

The researchers also found that if the maternal grandmother smoked, this increased by 53 per cent the risk of her grandchildren having a diagnosed autism spectrum disorder (ASD). "In terms of mechanisms, there are two broad possibilities. There is DNA damage that is transmitted to the grandchildren or there is some adaptive response to the smoking that leaves the grandchild more vulnerable to ASD," said one of the study authors Marcus Pembrey, Professor at University of Bristol in Britain. 

"We have no explanation for the sex difference, although we have previously found that grand-maternal smoking is associated with different growth patterns in grandsons and granddaughters," Pembrey said. For the study, published in the journal Scientific Reports, the researchers followed all the participants in Children of the 90s study.

Based at the University of Bristol, Children of the 90s, also known as the Avon Longitudinal Study of Parents and Children (ALSPAC), is a long-term health-research project that enrolled more than 14,000 pregnant women in 1991 and 1992.  It has been charting the health and development of the parents and their children ever since and is currently recruiting the children of the original children into the study. The findings suggest that if a female is exposed to cigarette smoke while she is still in the womb, it could affect the developing eggs -- causing changes that may eventually affect the development of her own children.