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Changes that occur during the menstrual cycle - Reproduction - KS3 Biology - BBC Bitesize
The menstrual cycle is an approximately 28 day cycle. Find out more with BBC Bitesize. For students between the ages of 11 and 14.
↗ https://www.bbc.co.uk/bitesize/topics/zybbkqt/articles/zvwb3j6