Under the Philippine Family Code, the prescriptive periods to impugn the legitimacy of a child are essential in cases where legitimacy is contested. Here is a detailed, meticulous breakdown of the relevant provisions under Civil Law > Family Code > Marriage > Paternity and Filiation > Legitimate Children regarding the prescriptive periods for impugning legitimacy.

Article 170 and Article 171 of the Family Code

Article 170: This article provides that only the husband may impugn the legitimacy of his wife’s child born during the marriage.
- Prescription Period: The action to impugn legitimacy must be brought within one year from the time of:
  - Birth of the child, if the husband was present in the place where the birth occurred.
  - Knowledge of the birth, if the husband was not present at the birth.
  - Return to the Philippines, if the husband was in a foreign country at the time of the child’s birth.
- Key Points:
  - This period is strict and cannot be extended; failure to file within this time results in a conclusive presumption of legitimacy.
  - The husband’s failure to file within the prescriptive period legally recognizes the child as legitimate.
Article 171: This article allows the legitimate child to impugn his/her own legitimacy but only in specific instances and within defined prescriptive periods.
- Grounds for Impugning Legitimacy:
  - The legitimate child may impugn his/her own legitimacy if there are physical impossibilities of sexual intercourse between the mother and the husband during the time of conception. This can be due to:
    - Husband’s physical incapacity.
    - Husband’s separation from the wife, such as incarceration or being in a distant place.
    - Serious illness preventing physical relations.
- Prescription Period: There is no explicit period for the child to impugn his/her own legitimacy, though procedural codes may require this action within the typical prescriptive periods for actions based on fraud or mistake.

Legal Grounds for Impugning Legitimacy

The legitimacy of a child can only be contested on grounds established by law. In addition to the physical impossibility of sexual relations, other specific grounds provided under the Family Code include:

Evidence of No Access:
- The husband must prove that he had no access to his wife during the period of conception. This can include proof of absence, lack of physical capacity, or other substantial evidence negating paternity.
Scientific or Medically-Based Evidence:
- Advances in DNA testing may serve as admissible evidence, provided it is legally obtained and properly presented in court. This may support the husband's claim if he can show, within the prescriptive period, that the child is not biologically his.

Other Rules on Impugning Legitimacy

Conclusive Presumption of Legitimacy: Under Article 164, children born or conceived during a marriage are presumed legitimate. This presumption is only rebutted if a legitimate ground exists, accompanied by proper action within the prescriptive period.
Strictly Construed Periods: Courts strictly apply the one-year prescriptive period, and any delay in filing an action to impugn may result in the automatic presumption of legitimacy under Philippine law.
Effect of Impugning Legitimacy on Rights:
- If legitimacy is successfully impugned, the child is classified as illegitimate and will be entitled only to inheritance rights as an illegitimate child.
- If the action fails, the child retains full rights as a legitimate child, which includes equal rights to inheritance and status.
Effect of Recognition by the Husband:
- If the husband explicitly or implicitly recognizes the child, such as by naming the child in official documents or publicly accepting the child as his own, this may prevent any subsequent action to impugn legitimacy. This recognition essentially acknowledges the child as legitimate, waiving the husband’s right to contest.

Recent Jurisprudence and Developments

Jurisdictional Requirements:
- Actions to impugn legitimacy should be filed in the Family Court, following proper venue and procedural rules.
Impact of Modern Technology:
- DNA testing, as a ground for impugning legitimacy, is increasingly recognized. However, it is crucial to file the action within the prescriptive period, regardless of technological evidence.
Constitutional Rights of the Child:
- Philippine law upholds the constitutional rights of children, including their right to legitimacy. Therefore, the courts require concrete, compelling evidence before depriving a child of legitimacy status.

Summary of Key Points

Who Can File:
- Primarily the husband, and in limited cases, the child.
When to File:
- Within one year of the child’s birth or knowledge of the birth (for the husband).
Grounds:
- Absence, physical incapacity, or other compelling reasons proving lack of access during conception.
Consequences of Failing to File on Time:
- The child remains legitimate and enjoys all associated rights.
Evidence:
- Strong evidence, such as DNA, but within the prescriptive period.
Recognition by the Husband:
- Any form of acknowledgment by the husband may prevent the future impugning of legitimacy.

This exhaustive understanding of the prescriptive periods to impugn legitimacy in Philippine law can guide practitioners and individuals in ensuring adherence to the Family Code provisions and recognizing the conclusive presumptions and limitations imposed by the law.