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Why can periods be irregular or heavy in the first years after menarche?
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menstruation
Cyclical changes during a woman's normal ovulatory menstrual cycle.
In the years immediately following menarche, it is common for menstrual cycles to be irregular or heavy. This occurs because the ovarian response to gonadotropic hormones can be erratic as the hypothalamus, pituitary gland, and ovaries continue to mature toward the cyclic activity characteristic of adult women.12
Because this hormonal regulation is still developing, the body may experience periods of imperfect ovarian functioning, which can lead to irregular or heavy bleeding patterns. This type of irregularity is typically a normal part of the maturation process and almost always disappears spontaneously as the reproductive system stabilizes.132