(1) A declaration of parental custody subject to a condition or a stipulation as to time is ineffective.
(2) The declaration of parental custody may be made even before the birth of the child.
(3) A declaration of parental custody is ineffective to the extent that a court decision on parental custody under section 1626a (1) no. 3 or section 1671 has been made or such a decision has been altered under section 1696 (1) sentence 1.