Selena Gomez is the "happiest girl in the world" because her mother is pregnant.

The 19-year-old star - who is currently an only child - is thrilled that she will finally be a big sister as her mom Mandy and stepfather Brian Teefey are expecting their first child together.

Selena tweeted: "Momma and Brian are finally letting me share the news... My mommys carrying my baby brother or sister :) I'm the happiest girl in the world! (sic)"

Mandy, a former actress, was married to Selena's father Ricardo Joel Gomez until the Disney star was five years old. She went on to tie the knot with Brian in 2006.

Selena - who is in a relationship with Justin Bieber - recently spoke of how she loves to spend time at home, revealing her hobby is baking.

She said: "I like to bake - cookies and cakes and stuff. I'm not that good but that's the whole fun of it; you get to mess around and experiment.

"It's nice to feel pretty and get dressed up but otherwise I'm definitely in jeans and my hair is up. I just like sitting on my couch watching movies."