Praise be to Allah.
If the woman is divorced by talaaq before the man has entered upon her and been alone with her, i.e., before intercourse or intimacy with her, then she does not have to observe any ‘iddah at all. Simply by virtue of the divorce it becomes permissible for her to marry another man. But if he has entered upon her and been alone with her and had intercourse with her, then she has to observe the ‘iddah (waiting period) which takes one of the following forms:
1 – If she is pregnant then her ‘iddah lasts until the pregnancy ends and she delivers, whether that is a long time or a short one. It may so happen that he divorces her in the morning and she gives birth at noon, in which case her ‘iddah is over. Or it may be that he divorces her in Muharram and she does not give birth until Dhu’l-Hijjah, so she remains in ‘iddah for twelve months. The point is that the ‘iddah of the pregnant woman lasts until she gives birth, no matter what the case, because Allaah says (interpretation of the meaning):
“And for those who are pregnant (whether they are divorced or their husbands are dead), their ‘Iddah (prescribed period) is until they lay down their burden”
2 – If the woman is not pregnant and she menstruates (is of child-bearing age), then her ‘iddah is three complete menstrual cycles after the divorce, i.e., her period comes then she becomes pure, then her period comes again and she becomes pure, then her period comes again and she becomes pure. That is three complete menstrual cycles, regardless of whether the time between them is long or short. Based on this, if he divorces her and she is breastfeeding and does not menstruate until two years later, then she remains in ‘iddah until she has had three menstrual cycles, so she may stay in this state for two years or more. The point is that she should go through three complete menstrual cycles whether the time involved is long or short, because Allaah says (interpretation of the meaning):
“And divorced women shall wait (as regards their marriage) for three menstrual periods”
3 – If a woman does not menstruate, either because she is very young or old and past menopause, then her ‘iddah is three months, because Allaah says (interpretation of the meaning):
“And those of your women as have passed the age of monthly courses, for them the ‘Iddah (prescribed period), if you have doubt (about their periods), is three months; and for those who have no courses [(i.e. they are still immature) their ‘Iddah (prescribed period) is three months likewise…”
4 – If a woman’s periods have ceased for a known reason and she will not menstruate again, such as if her uterus has been removed (hysterectomy), then she is like one who has passed menopause and her ‘iddah is three months.
5 – If her periods have ceased and she knows the cause, she should wait for the cause to cease and for her periods to return, then she should observe ‘iddah according to her menstrual cycle.
6 – If her periods have ceased and she does not know what caused that, then the scholars say that she should observe an ‘iddah of a full year, nine months for pregnancy and three months for ‘iddah.
These are the categories of ‘iddah for women divorced by talaaq.