I'm making the working assumption that a civil divorce has already been obtained with the intent of a religious divorce soon following. However, how critical is the timing of obtaining one insofar as future children are concerned? If a woman has relations with another man before obtaining a get, is she forever considered an adulteress and all her future children will mamzerut? Or, can she wait until she gets pregnant and then obtain it, or will the unborn child be a mamzer because the adultery is only established by conception? Or, is mamzer status conferred by actual birth only?
Does lacking a get affect children before conception, at conception, or at birth?
The answer is: At conception.
The problem of mamzerut is when conception of a child results from a specific kind of prohibited intercourse between a woman A and a man B: If the punishment for this intercourse is "Cut-of" (Karet) or death and when at time of intercourse, if B gives kiddushin to A, the kidushin are invalid "Ein Kiddushin Tofsim". (So a man with a single nidda, or his nidda wife, do not product mamzerim because kidushin with a nidda woman are valid.) This is the case here because A is already married to her husband and can not be "the property" of two husbands.
A question is: Are we sure that the child results from a relationship between A and B and not from a relationship between A and her husband?
- First, if people see that she is still cohabiting with the husband, in the same house, it may be that the rule of "רוב בעילות אחר הבעל", we rely on most relations having been with the husband, applies.
- Secondly, if she does not cohabit with B, but each of them lives alone, it may be that the child is not from B and is perhaps from a non-Jews, and according to Rabenu Tam, and I remember that the Halacha follows it, the child is not mamzer. I am not sure, but it may be that no chazaka (halachic assumption) links A to B.
- If A cohabits with B "as wife and her husband", the problem of mamzerut is very strong.
Anyway, the time of conception is looked for rules of Mamzer.
In Mishna, we see many cases of a widow or divorced woman that re-marries, and gives birth to a child. A doubt appears: Two possibilities.
- The child is born 9 months after intercourse with the first husband,
- or 7 months after intercourse with the second.