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" (Caret) or Death (Mishna Yevamot 49a) and when at time of because of the Isur Caret, if B gives Qiddushin to A, the Qiddushin are invalid "Ein Qiddushin Tofsin". (A man with a celibate Nidda doesn't product a Mamzer because he can marry her, "Qiddushin Tofsin". Therefore a man with his Nidda wife, does not product Mamzerim (Abaye in Gemara Yevamot 49ab, SA EH 4.13).) 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 is "רוב בעילות אחר הבעל", most of intercourses were with the husband, (Gemara Sota 27a, SA EH 4.15). We rely on most relationships having been with the husband,and the child its the son or the daughter of the husband.
- After the Get; if there is new offspring from the divorced or from the paramour are not Mamzerim (Yevamot 49b, SA EH in Baer Hetev sq 21 in name of the Chelqat Mechoqeq.), because the Isur is only an Isur Ase.
- 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 Gemara Yevamot 45b (and SA EH 4.19), 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 after which we decide for rules of Mamzer is the time of conception.
In Mishna, we see many cases of a widow or divorced woman that re-marries immediately after the death of her husband, 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.