Mary-Kate Olsen is reportedly pregnant.

The 22-year-old star, who shot to fame alongside twin sister Ashley in hit US TV show 'Full House' when they were just nine-months-old, has sparked rumours she is expecting her first child after her weight shot up to 102lbs, according to National Enquirer magazine.

A source said: "Mary-Kate has been looking a lot rounder recently. It is good she has put on weight, because she previously suffered from anorexia, but a lot of people think she could actually be attempting to hide her pregnancy."

Olsen has been dating New York artist Nate Lowman since the beginning of the year and is said to have been inspired to start a family by late actor and close friend, Heath Ledger ? who told her that becoming a father was the most rewarding thing he had ever done.

The source added: "Mary-Kate really took Heath's words to heart. She wanted the same kind of fulfilment in her life that Heath found in his after becoming a dad.

"She is really happy with Nate and is very excited they will soon be starting their family together."