Thousands of pro-life advocates have gathered on Parliament Hill for the 15th annual March for Life rally in the capital.

Rally organizers are expecting as many as 20,000 protesters to take part in what could be one of their largest rallies ever. Last year, close to 15,000 people participated.

Protesters are calling for abortion to be outlawed in Canada.

This year's demonstration comes weeks after a private member's motion requested a committee study to look into when exactly life begins.

The motion was introduced by Conservative MP Stephen Woodworth.

The Harper government has repeatedly said it has no interest in reopening the abortion debate.