Birth that occurred within the marriage duration or within 300 days of its termination or cancellation, as well as birth that occurred before the marriage, on condition that the child was registered after or at the moment of marriage registration (in the Civil Status Office).

• Act of 25 February 1964 - Family and Guardianship Code
  Place of publication: (Dz. U. z 2023 r. poz. 2809)