As a sworn translator for the language combinations Spanish-German and English-German, I carry out certified translations of birth certificates (Geburtsurkunden): Spanish-German, German-Spanish or English-German, German-English).
In Germany, you may be asked for a certified translation of a Geburtsurkunde for instance by the registry office (Standesamt) when you make your application for marriage (Anmeldung der Eheschließung), or when you wish to have your foreign marriage recognised, or when you make a declaration of birth (Geburtsanzeige) for a newly-born child. The citizenship office (Staatsangehörigkeitsbehörde) will ask you for a certified translation of your birth certificate for the process of naturalisation (Einbürgerungsverfahren). A certified translation of a birth certificate may also be required by other institutions, such as the immigration authority (Ausländerbehörde), or when you wish to register your children for school.
Birth certificates (Geburtsurkunde) and certified or attested copies of an entry of birth (beglaubigte Abschrift des Geburtseintrags) are issued from the register of birth (Geburtenregister) at the place of birth. In some countries, e.g. Nigeria, such registers have not existed for long, and people are required to make a Declaration of Age (eidesstattliche Versicherung über das Alter) before a notary public or other authorities.