23-time Grand Slam champion Serena Williams (pictured) pulled out of her fourth-round match at the French Open because of a pectoral injury on Monday afternoon, Paris time.

Williams was slated to play Maria Sharapova on Monday in the fourth round.  This is Serena's first Slam event since she gave birth to her first child last year.

It is unclear as to whether Williams will be healthy enough to play at Wimbledon, where she's won seven times.  This year's Championships begin on July 2nd at the All-England Club.