The Canadian women's hockey team took its worst beating ever from the United States and lost 9-2 to open the women's world hockey championship Saturday.

The Americans scored five goals in the first five minutes and 32 seconds.

Canada had never given up more than seven goals to the U.S. in 102 previous meetings.

Jocelyne Lamoureux scored a hat trick for the U.S, winner of the last three women's world titles. Twin sister Monique Lamoureux-Kolls and Hilary Knight each scored twice. Captain Julie Chu and Josephine Pucci also scored.

"To open the tournament against your biggest rival and put up a score like that, it's awesome for our team," said forward Kelli Stack, who had three assists. "We're going to remember this game."

Lamoureux-Kolls also had three assists for a six-point night. Molly Schaus stopped 19 of 21 shots for the win.

Toronto's Natalie Spooner and Marie-Philip Poulin of Beauceville, Que., replied for Canada.

"We have two choices," head coach Dan Church said. "We can wallow in our own self-pity or we can get back on the horse and go hard.

"I'm pretty sure the players are going to choose the latter and let this be something that helps us get better and we learn from it."

Fuelled by the adrenaline of playing a world championship on home ice for the first time since 2001, the Americans attacked from the opening faceoff and scored on their first shift.

The Canadians were completely unprepared for the pressure.

Canadian goaltender Charline Labonte was pulled at 3:32 of the first period after three goals on six shots. The Americans quickly scored twice in the next two minutes on Shannon Szabados.

Labonte, from Boisbriand, Que., went back in net for the start of the second period and made 15 saves on 22 shots overall. Edmonton's Szabados stopped nine of 11.

"It's a hard game to talk about because the score was just out of hand," Labonte said. "I'm probably going to watch all the goals and see what I personally could have done better."

The pain extended to more than the scoreboard for Canada. Forward Haley Irwin left the game midway through the first period with what appeared to be a serious right-leg injury. She fell hard into the boards behind the American net.

Irwin tried to hobble on one skate to the Canadian bench for almost a minute before the whistle mercifully blew and she could be helped off the ice.

Irwin immediately went to hospital for X-rays. Church would only say she didn't suffer a fracture and was not expected to play Sunday against Finland.

The Canadians seemed to have recovered for the second period when they outscored and outshot the U.S. But their defence fell apart again in the third and they managed just five shots on Schaus.

"We gave them space on the ice when they shouldn't have had it," Canadian captain Hayley Wickenheiser said. "Just making it way too easy for them."

The Americans blew holes in Canada's defensive zone coverage with speed and quick passes in the opening minutes. Their stretch passes created odd-man rushes. The U.S. outshot Canada 17-6 in the first period.

The tournament format is different this year with the top four countries — the U.S., Canada, Finland and Russia — in Pool A. Pool B is teams four through eight, which are Sweden, Switzerland, Slovakia and Germany.

The top two teams in Pool A earn byes to the semifinals. The bottom two meet the top two from Pool B in the quarter-finals.

After Finland on Sunday, Canada concludes the preliminary round Tuesday versus Russia.

"It's a disappointing loss for us, but fortunately it's not the one that really matters," Wickenheiser said. "We've got a lot of hockey left. Win or lose, it doesn't mean anything until you get to the big one, but we've got to get there first.

"When you get beat this bad, you've got to regroup and come back hard."

In the other Pool A games, Nina Tikkinen each scored twice in the third period to lead Finland to a 5-4 win over Russia. In Pool B games, Sweden defeated Slovakia 5-1 and Germany edged Switzerland 3-2.