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 | In females, changes in the primary sex characteristics involve growth of the uterus, vagina, and other aspects of the reproductive system. | |
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| Menarche, the beginning of menstruation, is a relatively late development which follows a long series of hormonal changes. | |
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| Generally, a girl is not fully fertile until several years after menarche, as regular ovulation follows menarche by about two years. | |
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| Unlike males, therefore, females usually appear physically mature before they are capable of becoming pregnant. | |
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| Changes in secondary sex characteristics include every change that is not directly related to sexual reproduction. In males, these changes involve appearance of pubic, facial, and body hair, deepening of the voice, roughening of the skin around the upper arms and thighs, and increased development of the sweat glands. | |
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| In females, secondary sex changes involve elevation of the breast, widening of the hips, development of pubic and underarm hair, widening of the areolae, and elevation of the nipples. | |
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