Grandmothers who smoked during pregnancy may have triggered autistic traits in their grandaughters, a new study suggests.

Scientists at the University of Bristol followed 14,500 participants in the Children of the 90s study, and found that that if a girl’s maternal grandmother smoked during pregnancy, she was 67 per cent more likely to suffer poor social communication skills and repetitive behaviours.

It also increased the risk of grandaughters being diagnosed with autism by 53 per cent.