I think the following:
In most states your husband is the legal father. You can not put the bio father on the birth certificate. You may be able to give the child the bio father's last name; some women use their own maiden name for the child. You can maybe put no father's name on the birth certificate. Once the child is born the bio father can file petitions (or you can; but then you pay) to have paternity testing done to establish his paternity and disestablish your husband's legal paternity. Your husband will be notified in prison of this process.