Delicate Situation

Hi my husband and I are the custodial parents of his 8 year old daughter. We believe we may be pregnant. This will be my first child. How would you suggest telling my stepdaughter as well as her mom. This is a delicate situation. We have created a very stable environment for my stepdaughter in our home (her dad has had her full time for 2 years now) and I fear that her mom might be more inclined to "want her back" because we're expecting. Please only comment if you have had this experience.