1. Certain women are excluded from the whole idea of predictable menstruation, therefore even if they previously had a fixed period they need not abstain from sexual intercourse at the times their fixed period was expected. Woman who are pregnant, nursing or who have passed menopause.
2. An elderly woman who has not menstruating three times when she expected to is considered not to be menstruating any longer and need not separate from her husband when she would have expected her fixed period.
3. Even if an elderly woman menstruated and become niddah she does not fix a new period and need not separate from her husband in anticipation of menstruation at any time. If, she has fixed a new period three times or has gone back to her old fixed period even once menstruating on the day of her old fixed period, she then returns to the ruling of any other woman who has regular periods. This is because it is then proven that when she previously stopped menstruating it was anomalous.
4. A pregnant or nursing woman does not have a fixed period for the whole duration of her pregnancy or her nursing.
5. A woman is considered pregnant after three months have passed without her menstruating, even if she has done a pregnancy test she should still abstain from sexual intercourse in anticipation of menstruation for these ninety days.
6. A nursing woman is considered to be nursing for 24 months after birth even if the child is weaned or even if the child is not nursing for some other reason.
7. If they menstruate these women separate like a woman who does not have a fixed period. (Interval, 30th day and hebrew date).
8. After three months of pregnancy the couple need not separate at the time that menstruation would have been expected.
9. After twenty four months have passed she should expect her previously fixed period to be reestablished. Therefore, if she has a period fixed for a day of the week or the month she separates from her husband the first time these days occur; if her period is for a fixed number of days upon having her first period she counts from there and separates at her fixed time.