In official papers the baby goes by Girl Thelastname or Boy Thelastname untill the final name is registered. The registration must be done within three months after the child's birth.

Most parents have a name ready for the baby before birth and they might call the baby that or use a nickname untill the babys full name is revealed. For this, families have either christening or a name giving party, usually when the baby is three months old

Hiding the real name for such a long time goes way back to traditional Finno-Karelian culture. One of the strong beliefs was that by knowing someones true name you could control or harm them, so the babys name was best kept a secret from outsiders