have approved i800a because pregnant what to do??

Hello My husband and I are currently adopting ...have already been matched and even have our i800. I have become pregnant and am kind of confused what I need to do. Has anyone had experience with this. We should pick our girl up prior to having our baby. Our agency is giving kind of confusing info. Do I have to get a whole new i800a even though the new child is not yet in our household. Do I just notify USCIS. I don't want to have to wait for a brand new i800a and pregnant is not one of the options on the USCIS supplement 3 form requesting an extension or change of status form. Any info would be MUCH appreciated!!!!