Brief Answer: GENERALLY 2 YEARS AFTER ONSET OF PUBERTY. Detailed Answer: Hello Thanks for writing in with your health concern. Puberty is defined as the entire spectrum of physical changes that occur in a boy or girl, to make their body capable of adult sexual functions and behaviour. Till puberty, the pituitary hormones that trigger off the ovaries in a girl, are suppressed by unknown chemicals that are still under research. Once the pituitary stimulating hormones get released, the ovaries release sex hormones, which bring about various changes. The first pubertal change is development of breast tissue , which on an average occurs at about 10 years ( happening to children at a younger age gradually ). Next the pubic hair starts developing, a few months later. Periods ( menstruation, or menarchae ) generally starts on an average two years after the breast bud starts developing. Thus 2 years into the changes that mark pubertal onset, a girl can expect her first period. These time ranges are highly variable and individual, affected by various factors , such as - race, nutrition, obesity, drugs, environment, psychological make up and genetic ( familial ) tendencies. All the best. Please feel free to discuss further.

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