US singer Alicia Keys is pregnant.

The star's spokespeople confirmed that she expecting her first child with boyfriend Swizz Beatz and is also engaged to the music producer.

The 29-year-old Grammy winner hid her bump under a flowery prom style gown by D&G at the Keep A Child Alive Black Ball in London on Thursday night. She has also been spotted in a series of tummy skimming outfits.

Keys and Beatz collaborated on the track Million Dollar Bill, which featured on Whitney Houston's comeback album.

The pair came out as a couple in May 2009. Beatz, who was going through a bitter divorce, denied reports that Keys had anything to do with the breakdown of his marriage.

He has two sons already, Kasseem Jr, from his marriage to Mashonda Tifrere and Prince Nasir, from a previous relationship.