Annamay Pierse shows off the silver medal she won Friday at the World Aquatics Championships in Rome. ((Clive Rose/Getty Images))

Canadian Annamay Pierse followed up her world-record effort in the semifinals with a silver medal in the women's 200-metre breaststroke final Friday at the World Aquatics Championships in Rome.

In a stunning finish, Pierse placed second in two minutes, 21.84 seconds.

Unheralded Serbian swimmer Nadja Higl shocked the field by winning gold in 2:21.62, while Austrian Mirna Ukic placed third in 2:21.97.

Pierse set the world standard, 2:20.12, during the women's semifinal heat Thursday.

"Tonight was a little bittersweet, coming in second," Pierse said. "To get a silver medal at the world championships is quite special.

"A world record is only someone's best time, so that can always get taken away from you. A silver medal from the worlds can never get taken away."

Toronto native Martha McCabe finished seventh in 2:23.36.

Olympic champion Rebecca Soni seemed to have the race in hand. The American got off to a world-record start and built a two-body-length lead by the final turn.

However, Soni inexplicably slowed down with about 25 metres to go, allowing Higl, Pierse and Ukic to pass her before the finish.

The three athletes then raced to the wall, with Higl just edging out Pierse for the gold.

"I can't recall a swimmer at a major event misjudging a race by that much," CBC Sports swimming analyst Byron MacDonald said of Soni. "This just doesn't happen."

Pierse, a Toronto-born swimmer who now lives in Vancouver, kept up her pace despite Soni's explosive effort through the first two-thirds of the race.

"I've raced her a lot and I kind of learned a little bit about her strategy," Pierse said. "She is not as good at holding if she goes out that fast.

"When I saw how far ahead she was, I thought, 'Oh my goodness,' but I refocused myself. I got back in my own rhythm and my own race."

The 25-year-old won Canada's second medal in the pool.

Victoria's Ryan Cochrane earned a bronze medal in the men's 800 freestyle on Wednesday.