Serena Williams arrives at the 19th Annual Elton John AIDS Foundation's Oscar viewing party held at the Pacific Design Center on Feb. 27, 2011 in West Hollywood, California.

*People.com is reporting that Serena Williams suffered a pulmonary embolism last week that resulted in a hematoma, which had her in a Los Angeles hospital on Monday – the day after she attended both the Elton John AIDS Foundation Academy Awards Viewing Party and the Vanity Fair Oscar party. [See photos.]

“Monday Serena Williams underwent emergency treatment at Cedars-Sinai Medical Center for a hematoma [collection of blood within the tissue] she suffered as a result of treatment for a more critical situation,” the rep told People.com.

“Last week, Serena suffered from a pulmonary embolism [a blood clot in the lungs] which was discovered upon her return to L.A. She had been in New York for doctor appointments for the ongoing issues with her foot.”

The rep added, “Doctors are continuing to monitor her situation closely to avoid additional complications.”

Williams, 29, had been spotted at Cedars-Sinai several times over the past week, according to People.

Serena Williams arrives at the Vanity Fair Oscar party hosted by Graydon Carter held at Sunset Tower on Feb. 27, 2011 in West Hollywood, California.