If a woman finds anywhere on her body or clothing a stain that may be blood and that cannot be attributed to some other source, she must assume that it may have been menstrual blood unless it is found in a place where it could not have come from her womb, or on colored clothing or on an object that is not susceptible to impurity (190:1,5-32,39-53). On special rules if the woman is young see 190:2-4. On special rules for stains found on material which she used for examining herself see 190:33-38; many authorities hold that only such stains are counted in establishing a regular period (190:54). On the desirability of frequent self-examination see 196:9; on special classes of women see 196:7-8.
A bride must observe seven (or more) clean days beginning with the day her wedding date is finally set. During these days she should examine herself daily (or at least once) and she should immerse herself within three days of the wedding (not necessarily at night; see 197:3). If she is a NIDDAH at the time of the wedding she is not allowed to be alone with her husband until after she immerses herself (192:1-5). If she is a virgin, after the first time she has relations she must wait four days and then count seven clean days; during this time she is regarded as a NIDDAH even if she has not bled (193:1).
A women who has miscarried or given birth is treated like a NIDDAH from the time the birth begins even if she has not bled; see 188:3. She must count seven clean days after the day of the birth, and if the child is a girl or its sex is not known (provided the pregnancy lasted at least 40 days) she must not immerse herself until at least 14 days after the birth (194:1-13). These laws do not apply to a woman who has a Caesarean section (194:14).
When a woman is a NIDDAH her husband is allowed to be alone with her (provided the marriage has been consummated), but he is not allowed to touch her or to hand or throw anything to her, or to sit on her bed even in her absence, or to eat or drink from her plate or cup in her presence, or to look at parts of her body that are usually covered (195:1-7). It is preferable that she dress in a special way while she is a NIDDAH (195:8-9). She is not allowed to make his bed or to pour water in his presence for him to wash with, and they are not allowed to pour drinks for or directly send drinks to one another (195:10-14). However, they may take care of one another when they are sick if there is no one else to do so (195:15-17). A husband should have relations with his wife before he goes on a trip (184:10); he may take her word that she is not a NIDDAH (see 185:1-4).
Shulchan Aruch, Copyright (c) 2000 ProjectGenesis, Inc.