Last name issue...

Natalie
So I am previously divorced with a 7yo daughter. I kept my married last name to match her (for school). Well now I'm expecting and I'm not sure if I should give the baby my married or maiden last name? And if I give my maiden last name, should I go back to my maiden name? 
The father is up in the air and may not be involved. If he gets involved then it will be a different story. 
Any suggestions would be appreciated