Pop star Britney Spears is pregnant with her second child by husband Kevin Federline, US Weekly reported Tuesday.

Spears, 24, was seen by the pool at Caesar's Palace in Las Vegas last weekend, sporting a red bikini and "a serious bump," the magazine said on its Web site.

Sources confirmed the pregnancy, US Weekly said.

The couple married in September 2004 and have a son, Sean, who is 7-months-old.

Federline has a daughter, Kori, 3, and a 21-month-old son, Caleb, from a previous relationship.