March 2, 2011 -- Tennis player Serena Williams was rushed to a Los Angeles hospital Monday to undergo emergency treatment for complications from an earlier pulmonary embolism -- a blockage in an artery of her lung.

"Thankfully everything was caught in time. With continued doctor visits to monitor her situation, she is recuperating at home under strict medical supervision," Nicole Chabot, Williams' publicist, said in a statement.

A pulmonary embolism is a clot that lodges in the lung but originated elsewhere in the body. The most common source of the clot is deep vein thrombosis in the leg.

If left untreated, the mortality rate is roughly 30 percent, according to the Centers for Disease Control and Prevention.

Chabot said the embolism was discovered shortly after Williams returned to Los Angeles from New York, where she had been visiting doctors about a foot injury. Williams reportedly cut her foot on a piece of glass at a restaurant in July. It required two surgeries.

Because of Williams' recent injury and the long flight from New York to L.A., she would have been at risk for deep vein thrombosis, according to Dr. Mark Adelman, Chief of Vascular Surgery at NYU Langone Medical Center.

"Prior surgery, air travel, prolonged sitting, birth control pills, obesity and pregnancy can predispose a patient to a blood clot in the leg that can travel to the lung," Adelman said.

Pulmonary embolism is surprisingly common, Adelman said.

"I treated three blood clots in the lung today. There are tens of thousands blood clots in the lungs that happen each year in the United States."

Williams was likely treated with blood thinners and possibly clot-busting drugs called embolytics. Both of these would increase her risk for hematoma – the buildup of blood outside of a blood vessel that landed her in the hospital Monday.

"The hematoma was another unexpected scare that was subsequently removed," said Chabot.

Hematomas can range in severity from a mild bruise to a serious hemorrhage.

"This has been extremely hard, scary, and disappointing," Williams said in a statement. "I know I will be OK, but am praying and hoping this will all be behind me soon."

Serena Williams Hospitalized

The effects that the embolism and the hematoma could have on Williams' athletic career remain unclear. But Dr. Andrew Gregory, an expert in sports medicine at Vanderbilt University Medical Center in Tennessee, said they could affect her ability to breathe and make her more susceptible to bruising and bleeding -- both of which could hurt her performance on the tennis court.

"While I can't make any promises now on my return, I hope to be back by early summer," Williams said in a statement. "That said, my main goal is to make sure I get there safely."