There are different situations that involve questioning the legitimacy of a child. In fact, a birth certificate can be cancelled if there's adequate proof that it is fictitious. Another situation in which the legitimacy can be questioned is when the child was conceived as a result of artificial insemination. Both the husband and wife should prove that insemination was approved otherwise, the wife will be sentenced as an adulteress.
Even if the husband and wife are married, the husband can still question the child's legitimacy based on the following grounds:
Art. 166
(1) That it was physically impossible for the husband to have sexual intercourse with his wife within the first 120 days of the 300 days which immediately preceded the birth of the child because of:
(a) the physical incapacity of the husband to have sexual intercourse with his wife;
(b) the fact that the husband and wife were living separately in such a way that sexual intercourse was not possible; or
(c) serious illness of the husband, which absolutely prevented sexual intercourse;
(2) That it is proved that for biological or other scientific reasons, the child could not have been that of the husband, except in the instance provided in the second paragraph of Article 164; or
(3) That in case of children conceived through artificial insemination, the written authorization or ratification of either parent was obtained through mistake, fraud, violence, intimidation, or undue influence.
Who may question legitimacy
Art. 170. The action to impugn the legitimacy of the child shall be brought within one year from the knowledge of the birth or its recording in the civil register, if the husband or, in a proper case, any of his heirs, should reside in the city or municipality where the birth took place or was recorded.
If the husband or, in his default, all of his heirs do not reside at the place of birth as defined in the first paragraph or where it was recorded, the period shall be two years if they should reside in the Philippines; and three years if abroad. If the birth of the child has been concealed from or was unknown to the husband or his heirs, the period shall be counted from the discovery or knowledge of the birth of the child or of the fact of registration of said birth, whichever is earlier.
Art. 171. The heirs of the husband may impugn the filiation of the child within the period prescribed in the preceding article only in the following cases:
(1) If the husband should die before the expiration of the period fixed for bringing his action;
(2) If he should die after the filing of the complaint without having desisted therefrom; or
(3) If the child was born after the death of the husband.
