Babies Last Name

The father of my unborn daughter recently told me that he will not be signing the birth certificate until after we have a paternity test. We have decided to have a private paternity testing facility to come to the hospital as soon as the baby is born to perform the test but the results might not come out until after I have left the hospital. I was informed that he can sign the birth certificate and affadict of paternity after the baby is born, up to 60 days later I think. So my question is who's last name should I put on my daughters birth certificate?