“About three months later, Yehudah was told: ‘Your daughter-in-law Tamar has played the harlot’” (Bereishit 38:24). Based on this, we can conclude that a woman’s pregnancy becomes noticeable after three months. Therefore, a woman must wait three months after being divorced or widowed before she can remarry. This is to ensure that if she becomes pregnant, we can be certain of who the father is. Usually, the waiting period does not pose a difficulty for the woman. It can actually be quite positive, as it allows for a needed break between two chapters in her life, a sort of “time out.”
However, there are some cases where this requirement is problematic, such as the following case.
The law of a three-month separation and waiting period applies to a woman who converts to Judaism. This is so it will be clear whether she conceived before or after her conversion. A minority opinion disagrees and maintains that the separation and waiting period does not apply to a woman converting to Judaism. The logic behind this is that once she decides to convert, she will make sure to avoid getting pregnant before her conversion, and therefore she is permitted to marry immediately. Now, let us say that there is a non-Jewish couple who have both decided to convert. Would they be required to separate for three months? The minority opinion agrees that they are required to separate. This is because the logic above applies only to a situation in which a woman is converting alone. In contrast, in the case of a couple converting together, one might argue that since they are used to living together and will continue to do so after they convert, she will not view the conversion as a major turning point in the same way the single convert will (and thus will not resolve to avoid pregnancy before conversion). Thus, she is required to wait three months after her conversion before returning to live with her husband.