Which father is my real father?: Japan's 300-day rule

In early May, the Japanese government announced that it will take a special measure to recognise children born within 300 days of their mother's divorce, given that the mothers became pregnant after divorce. This announcement came after a group of divorced women with children raised the issue on the current civil law, sparking debate in the National Diet.

Section 2 of Article 772 of the Japanese Civil Code, implemented in 1898, stipulates that a child born 200 days or more after its mother's marriage took place, or within 300 days after its mother's marriage was dissolved or terminated, is considered to have been conceived during her previous marriage. This means that the child must be added to the koseki of its mother's previous husband, or family registry, which causes tremendous distress for the mothers and other people involved. In order to prove that the child is not biologically related to the former husband, this former husband has to testify before the court. Many of these mothers avoid contact with their former husbands, or do not want their children to be registered in their former husbands’ registries. In such cases, children do not have koseki.

The Ministry of Justice estimates that approximately 3,000 children are born under these circumstances every year. Those children who do not have family registries cannot receive various social services such as health care and pension programs, and are not issued passports.

Following the government's announcement, the issue has been extensively debated on many blog sites. An anonymous blogger argues that the law does not need to be changed.


If a woman insists that her kid is her new husband's, then think about the situation carefully. The woman had a new boyfriend right after (maybe like the day after) her divorce, got pregnant and remarried. Does it sound possible? What is clear is that this woman was conducting acts of infidelity before her divorce. Even if not, what's up with getting pregnant so soon after divorce? I can only think that this is their own fault. Is there anything wrong with this law?


Another point, apparently the period women are not allowed to get remarried has been shortened from 180 days to 100 days. Getting remarried in three months will propbably end up in another divorce, won't it? Marrying someone you don't really know that well… If they insist that they know each other well, then I would suspect a case of infidelity. This kind of law is not good enough. In fact, I think they should be restrained. For instance, if a woman gets divorced and she has children, then she shouldn't be able to remarry, or something like that. Almost 100% of all cases of abuse we see on TV news happen in households with divorced parents or unmarried couples living together. Clearly, there is a risk in remarrying with children. Innocent children are betrayed and abused by their own parents whom they trust. Isn't this situation much more serious?

On the other hand, Toranekojiji writes that the law is behind the times and calls for affirmitive relief.



This “300 day rule”, which determines the father of a child born after its mother's divorce, inherits the substance of the Civil Code written in the Meiji era. It is based on the average gestation period. However, even in cases of conception after a divorce and preterm delivery, short of “300 days”, a child is regarded as an offspring of her former husband's.

Divorce is not necessarily granted easily. It is not rare that divorce mediation can drag on in such a case as a woman is running away from her husband's violence.




Even in the case of conception before a divorce, it must be possible to determine the father of the child based on DNA testings, arbitration records, and residence registry showing the state of separation.

In the revision by the Ministry of Justice, if a woman obtains a doctor's note proving that she got pregnant after her divorce, then her child will be regarded as either her new husband's child or an illegitimate child. Although it is a step forward, not a lot of cases will not be solved by this.

A bill which takes into account revision of pre-divorce pregnancy situations has been held back by the conservatives with reactionary family values. Justice Minister Nagase Jinen brought up the argument of “fidelity and sexual morals”. There was backlach within the Liberal Democratic Party over the insertion of a shorter restrictive period for women to get remarried.



We should redress situations where women who suffered through their divorce have to suffer again over her child's koseki. We should not conclude the issue based on the recent revision, but should develop this discussion in more depth towards amending the law to help more mothers and their children.

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