Foster, 37, checked into the Sao Rafael Hospital on Feb. 6 for a "simple liposuction," says Ellen Dastry, spokeswoman for plastic surgeon Silvio Sterman.
Foster went into cardiac arrest while being anesthetized, "but was revived in less than a minute by heart massage," Dastry adds.
See the day's top news stories.
She was then placed into an induced coma before being transferred into an intensive care unit "to avoid unnecessary complications."
She's currently recovering in Sao Paulo's better-equipped Sirio-Libanes Hospital, added Dastry, who did not release any additional details.
Usher , 33, cancelled his performance at Clive Davis' pre-Grammy Gala last Saturday to rush to Brazil to be with his wife. His rep told Usmagazine.com Monday that she was in "stable condition after suffering complications from routine surgery."
See what the stars wore to the Grammys.
Foster and Usher wed in August 2007. They are parents to two-month-old Naveid Ely Raymond and Usher Raymond V, 15 months. Foster also has three sons from a prior relationship.