Teen star Jamie Lynn Spears' mother has let it slip that the pregnant actress is expecting a baby girl.

The 17-year-old star stunned the world when she confirmed she was expecting her first child in December (08), and now her mom Lynne has been overheard telling friends the baby will be her first granddaughter.

A source tells America's Life + Style magazine, "I heard Lynne talking about Jamie Lynn's baby. She said Jamie Lynn and the baby's dad (Casey Aldridge) were so excited when they found out it's a girl."

The proud mum, who is grandmother to eldest daughter Britney Spears' two sons - Sean Preston and Jayden James, also gave up Jamie Lynn's nursery secrets.

The witness adds, "She is going to do the nursery in white, black and yellow."

The baby is reportedly due on June 29th.