Thesearchguru is a search consultant that has helped several people on the forum. She has posted threads with helpful information for searching in each state as well as information on the best way to post in the forum - include DOB, sex, city/state in the title of the thread. You can contact her through her website
http://www.therighttoknow.info
Are either of your niece's bparents still alive? How old is your niece? If you know the name of the agency that handled the adoption they might forward a letter with the updated medical information.
Good Luck!