Finland
The default in Finnish law as of 2018 is that the husband is the acknowledged father of the child who is born into wedlock (or to a deceased husband). Only if the wife agrees, can that initial determination be set to something else. However, from 2016 the general right the mother to solely allow or prevent the parental investigation was abolished. The default and immediately forcing juridical assumption of paternity of a husband was not changed in the latest 2015 act.
A man can bring up a later legal action to annul his paternity, disregarding of the resistance of his wife. The legal action for annulment may be brought in the district court by a man whose paternity has been determined on the basis of either marriage or by some other authoritative decision. However, the ruling of the court can be pretty much anything and the UN declaration of children's rights are not followed.
A man who has officially acknowledged paternity relinquishes his rights to further actions if he, knowing the woman had a sexual intercourse with another man, or that she has used foreign sperm for fertilization, has stated in writing following birth of the child that the child is biologically his.
Otherwise legally binding prebirth acknowledgment of a man must be rejected, if either the health care staff of the child supervisor do have a founded suspicion that the man is not a father of the child, or he is for any reason not capable to understand what he is doing when acknowledging the paternity.
If a mother deliberately gives false information to the authorities, which contributes to the erroneous establishment of paternity, she may be fined