Ovulation during menstrual bleeding is quite rare, but it can happen on time if you have a shorter cycle, more days of bleeding, or an irregular cycle.
The menstrual cycle starts on the first day of bleeding and usually lasts 28 days, but 21 to 35 days is considered normal. Menstrual bleeding usually lasts between 3 and 7 days.
The first phase of the menstrual cycle is known as the follicular phase and is variable for each woman and each cycle is about 14 days long. It is the phase during which menstrual bleeding starts and follicular growth begins, one of which is selected as the dominant follicle. The selected follicle grows rapidly and by hormonal mechanisms' ovulation occurs. It is then that the luteal phase begins which has a more stable duration of 14 days.
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