Anovulatory cycle
While the normal menstrual cycle in the human typically lasts 4 weeks (28 days, range 24–35 days) and consists of a follicular phase, ovulation, and a luteal phase, followed by either menstruation or pregnancy, the anovulatory cycle has cycle
lengths of varying degrees. In many circumstances, menstrual intervals are prolonged exceeding 35 days leading to oligomenorrhea (cycle >35 – 180 days interval), or even longer, amenorrhea. In other cases, menstruation may be fairly regular (eumenorrhea), or more frequent (intervals < 21 days), or there may be a loss of menstrual pattern (menorrhagia, dysfunctional uterine bleeding).
Khul'
When a woman is granted a divorce through khulʿ, she must enter a waiting period known as iddah. During this period, a woman is not allowed to remarry for one menstrual cycle to ensure that she is not pregnant. In case of divorce women has to wait for three menstrual cycles. Most jurists recommend waiting for the three menstrual cycles even for the iddah of a divorce through khulʿ. If a woman has already gone through menopause, she must wait three calendar months. The waiting period for a woman who has irregular periods is dependent on different interpretations. While some jurists believe that a woman should observe the waiting period for three calendar months as well, others believe that a woman should observe the waiting period for nine months. If a woman is pregnant or becomes pregnant during the waiting period, she must observe the waiting period until laying her burden.