A/an may involve anything from a minimal exchange of information to extensive contact with the birth mother before and after the child is born.

The correct term to fill in the blank would be "oprn adoption". An open adoption may involve anything from a minimal exchange of information to extensive contact with the birth mother before and after the child is born. It is a form of adoption wherein the adoptive families and the biological family would have rights to a certain degree of the personal information of the adoption process and having an option of contract. In this type of adoption, the adoptive family would have all the rights to be the legal parents however the biological could have a the right to have a contract in different forms like sending photos of the child, personal visits and sending messages. 

Where are they though?