Go to check in the own Town Hall, about the proof you need to have a Birth Certificate. Our town asked for affidavit of some people that saw you pregnant (2 people, I think), affidavit from the people who witness the birth (2 people, and/or DH), some prenatal care proof, like ultrasound, etc. and letter for the pediatrician that say age, name and state of health of baby.
The only big issue for us, was that i forget to about the birth certificate at all during the pregnancy. At 5 days postpartum, I concern about it.At day 6 or 7 DH when to the town hall asking for the forms,etc. There is suppose a date line of 10 days after the baby born to fill up the application. We're running to put all the papers together, in two days...After all, everything were fine...
Best luck for you...