Breasts are the only external human organs whose shapes and sizes change so frequently. Even during the monthly menstrual cycle of the female, there are marked changes in the bulk and texture of the breasts. This is an ongoing process. The breasts change their shapes through the cycle and then return to almost as they were when the cycle ends. In most women, the changes are unnoticeable, but some women can clearly see the changes as their month advances.

The menstrual period is only one of the factors that affect the sizes and shapes of the female breasts. There are many more such periods in a woman's life. Changes are seen in the breasts when the woman loses her virginity, when the woman becomes pregnant, all through the pregnancy, during the lactation, when the lactation stops, during menopause and finally when the woman reaches her old age. As the woman grows, the breasts also grow along with the woman. If we were to plot a graph of the woman's growth with her breasts' growth, then there would be obvious similarities to be seen.

The first changes in the breasts are seen when the girl reaches her puberty, which could be anytime after eight years. Actually this is when the girl actually gets breasts, for they were just a pair of nipples on the chest until that time. With puberty, hormones like the estrogen trigger the growth of the breasts. The breasts begin to become rounder in shape, the nipples become more prominent and the areolas widen and darken.

Breasts keep on developing all through the puberty. They never actually settle into one final shape until the woman becomes pregnant for the first time. This is when the pubertal changes come to an end and the changes due to pregnancy begin to take place. During pregnancy the breasts tend to become bulkier and rounder. Hormones need to trigger the breasts to get ready for the lactation that is to come. So in preparation, the breasts begin to attain their maximum possible size. Just a couple of days before childbirth, the areolas could become wrinkled and the milk may begin to ooze out of them. Lactation gives breasts their most functional shape. The breasts become tauter so that the nipples could be easily accessible to the infants. There is also an increase in the length of the nipples due to the infant continually suckling on them.

But it is fascinating to know that no two women will have the same kind of changes during their pregnancies. In some the breasts could even sag due to the infant's constant pulling action on the breasts in the downward direction. During lactation women tend not to wear bras due to the inconvenience they cause which suckling the baby. Due to this the breasts may sag more.

Also, in a woman, the breasts will not look the same during all her pregnancies. Changes are more marked during the first pregnancy, because this is when the hormones need to trigger the breasts to be ready for further changes. Such hormonal triggers are not necessary during successive pregnancies.

After the baby is weaned, the breasts remain more or less constant in their size and shape (except for the menstrual changes) until the woman reaches her menopause. Menopause is when the woman's menstrual periods stop, which occurs generally after the age of forty years. After menopause, the breasts lose all their functional purposes. Breasts could become wrinkled, droopy or sag down after the menopause. The skin over them could lose their texture. This is the time when the breasts are moving towards their old age.

All the above discussed factors were hormonal in nature. These are the changes that are normal to all women, and happen as their age advances along. But it must be noted that there are several external factors which could also play a determining role in giving shape to the breasts

The bras that a woman wears are perhaps the most important factor. Bras are responsible for holding the breasts most of the time, and hence the final shape of these flexible but delicate organs tends to be how the bra decides. Bras should neither be too tight nor too loose. This could play havoc with the shape the breasts get. Corsets and tight bras could retard the circulation in the breasts and spoil their texture.

Women who take hormone pills and contraceptives are prone to have changes in their breast sizes. The contraceptive pill could bring about a temporary increase in the size of the breasts.

Exercise is another way to change the shape of the breasts for the better. Pectoral and upper torso exercises improve the quality of the muscles under the breasts. This finally helps to make the breasts firmer. In a very like manner, the amount of massaging that is done on the breast - either by herself or by her sexual partner - could help improve the circulation of the breasts and improve their shape.

Shapes of breasts are many a time hereditarily determined. A girl tends to develop the kind of breasts her mother has. But with regular massage and exercise, the shape of the breasts can be improved.