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Your cycle length

• This whole process takes around a month, and so the interval between menstrual periods is most commonly about 28 days.

• In some women, the cycle can occur every 21 days while in others it may take up to 35 days. So the normal range for the menstrual cycle is between 21 and 35 days.

• Day 1 of a cycle is the first day on which menstrual bleeding will occur.

hormone called progesterone. (Progesterone is only made after an egg is released.) It acts on the lining of the womb by stopping its thickening at the right stage. It also improves the endometrium’s blood supply and makes it a suitable and ‘comfortable’ environment for the fertilized egg to implant.

If a fertilized egg does not implant, the production of progesterone from the ovary falls sharply. As these hormone levels fall, the blood supply to the lining of the womb is reduced and the endometrium is shed. This results in the bleeding that we know as a period. The cycle then starts over again.