Is it possible for intercourse and pregnancy to occur during the period of purity between two menstrual cycles, and does "menstrual cycle" only refer to the period of bleeding, or is there a stage that precedes it, and how can intercourse take place without pregnancy without using a condom?

Scholars have differed regarding the minimum and maximum duration of menstruation. The preponderant opinion is that its minimum duration is one day and one night, its usual duration is six or seven days, and its maximum duration is fifteen days. Anything beyond that is considered istihada (non-menstrual bleeding). It is impermissible to engage in intercourse with a menstruating woman before the cessation of blood flow within these fifteen days. The minimum period of purity between two menstrual cycles is fifteen days. The last day of purity before the onset of bleeding is considered part of the days of purity, and intercourse is permissible on it, leading to pregnancy. Permanent birth control methods are forbidden, while temporary ones are permissible.