TORONTO - Statistics Canada says the proportion of first-time births to older moms -- those 35 and up -- almost tripled from 1987 to 2005 in Canada, from four per cent to 11 per cent.

A study of their children finds that they don't differ significantly in terms of health, behaviour and cognitive abilities from children born to younger mothers aged 25 to 29.

They were just as likely to be in excellent or good health up to the age of five, and timing was similar for the incidence of asthma, saying their first word and taking their first step. Their scores were also similar for vocabulary and number knowledge.

But the statistics showed a few differences: the kids of older mothers were more likely to be late to first sit up by themselves, to score lower on the motor and social development scale at ages two to three, and to have lower positive behaviour scores at ages four to five.

Almost a quarter of the children of older moms had a mother who suffered from hypertension during pregnancy, compared to 13 per cent of children with moms in the 25-to-29 age group.

About 40 per cent were delivered by C-section, compared to 23 per cent of the children of younger moms, and more were born pre-term.

A higher proportion of kids born to older moms were breastfed -- about 43 per cent were nursed for more than six months compared with about one-quarter of children of the younger group of mothers, Statistics Canada said.

During the same period studied, the proportion of first births for women in their early 30s rose from 15 per cent to 26 per cent.