Expanded family leave policies, while they often take employees out of the labour force for longer periods of time, can be a boon to the new mothers' careers, according to a new study.

"Maternity leaves, if they offer job protection, can help women who have children improve their job continuity and eventually their economic outlook," said the lead author of the project, Professor Michael Baker of the University of Toronto.

Researchers looked at Canadian leave policies and employment among new mothers in Canada from 1976 to 2002.

As Canadian provinces expanded leave rights from 17 or 18 weeks in the mid-1980s to at least one year in the early part of this decade, the number of new mothers on leave months after having given birth expanded dramatically. For example, a province that instituted a mandatory 18-week leave could expect an increase of 5.5 percentage points in employed mothers who took leave in the month of their child's birth.

And leave extensions expanded the return of mothers to their pre-birth employer, whereas before more of those mothers would have taken part-time work somewhere else or stayed home, Baker said.

"The argument is, if women have more continuity, in the longer run they'll have better wages," Baker said.

The study, "How does job-protected maternity leave affect mothers' employment?" was published in the October issue of the Journal of Labor Economics.