Psychologists said their research showed that there were many "positive outcomes" for both mother and child related to having children later in life, and suggested that this was helped by the role older fathers played.
The number of births to women over 40 has increased by 50 per cent in the past decade, and the findings are part of a study of more than 100 women to find out what effect late motherhood has on children. The mothers were first studied when their babies were born and are now part of a subsequent study into four-year-olds.
Dr Julia Berryman, the author of the report, said: "We looked at the way parents played with their children and found that while older and younger mothers did not differ in terms of physical or sedentary play - such as reading or doing jigsaws - partners of older mothers tended to do more sedentary play with their children than younger fathers.
"We can't say for certain, but this could be a reason why the children's vocabulary is more extensive."
The researchers at Leicester University also found that older mothers were more likely to breastfeed their babies and breastfeed them for longer, which is known to promote optimum development for the child.
Another difference linked to maternal age was that children of younger mothers saw grandparents and other members of their extended family more frequently than did children of older mothers.