1,076. No Fixed Pattern

154:6 A woman who has no regular menstrual pattern should check herself before and after having marital relations. Also, her husband should clean himself after relations to make sure there is no sign of blood. However, when she is presumed not to have her period, such as if she is pregnant after the first trimester, nursing or post-menopausal, then she need not check.

154:7 There are women who don't have a set menstrual pattern but they do have a known number of days in which they will not see blood. For example, she has determined that she will not see blood 25 days after she last saw it, only later than this. She therefore does not have a fixed time because sometimes it's a day later, sometimes two days, and sometimes three. Since this has happened three times and established a presumption, such a woman is considered like one with a regular pattern until the twenty-fifth day. After that, since she might or might not see blood, she has no presumption of menstrual purity and may not engage in marital relations.