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Why your breasts increase and decrease over your life

A woman's breasts are changing all the time. They change during puberty, menstruation, pregnancy, breastfeeding, and menopause. The breast consists of fat tissue with lobes connected by a suspensory ligament. The breast sits on top of muscles that lift it up. There are also milk ducts in the breast that lead to the nipples. With every step you take, the muscles squeeze the milk ducts to push milk towards your nipples, where it can flow out into your baby's mouth. The whole structure is wrapped in skin that contains stretch receptors that are stimulated by breasts growing or shrinking.

The scientific name for breasts is mammary glands. They are so named because they produce milk (Greek: mama). All female mammals have mammary glands and produce milk.


During puberty, the hormones oestrogen and progesterone cause all women to develop breasts. The size of a woman's breasts is mostly determined by her genes; however, body weight does play a role as fatty tissue will make smaller breasts look larger and vice versa. During puberty, the glands that produce milk are stimulated to grow by oestrogen.

Breasts start dropping towards the end of puberty when the body starts producing less oestrogen and progesterone. Milk ducts are also shrinking due to this hormonal change. The suspensory ligaments holding up the breast are not affected by these hormones so they do not shrink or stretch. With no support from the surrounding tissues, the breasts sag over time, eventually resulting in what is commonly called "droopy boobs." Some women's breasts never sag because their suspensory ligaments are stronger than average; for other women it will happen much earlier in life.


Breasts may become enlarged during pregnancy, especially if you are expecting more than one baby at a time. The extra breast tissue that develops for breastfeeding will usually go away after the baby(s) is (are) weaned, but sometimes it can leave behind scar tissue that looks like dimpled skin on the breasts. This can be caused by the development of excess breast tissue that leaves behind extra amounts of supportive tissues along with stretch marks.

Another important hormone that affects a woman's breasts is prolactin.[1] This hormone is released during breastfeeding and stimulates the growth of milk ducts in the breast. Prolactin also causes lactation (production of milk) by causing cells around the milk ducts to produce milk. The more children a woman has, the more prolactin her body produces, enlarging her breasts with each pregnancy; this is why women who have more children tend to have larger breasts. During breastfeeding, prolactin levels can be as high as 100 ng/ml.

After the first pregnancy and birth of a baby, some women's breasts do not return to their previous size. They may even continue growing larger or stay enlarged for as long as they breastfeed the baby (up to around 5 years). This is due to the effect of breastfeeding on prolactin levels. Prolactin stimulates breast growth and can cause them not to shrink back down, even if a woman does not have any more children after the first one(s).

Breasts always grow during pregnancy because oestrogen and progesterone encourage their growth as well as milk duct growth. There is an increase in fatty tissue production as well, which serves as a milk source for the baby after birth.

During pregnancy, the ligaments that hold up your breasts become looser to prepare them for breastfeeding once the baby is born. This gives your breasts more of a "jiggly" quality because they are made up of fatty tissue and lack a lot of the connective tissue that sagging breasts have. After giving birth, some women notice their breasts look more droopy than they did before pregnancy because they no longer carry as much fatty tissue.

During breastfeeding, hormones from prolactin also cause the milk ducts to be stimulated and grow bigger in preparation for milk production. Prolactin levels are high, which causes the breast to be full of milk and feel heavy in preparation for breastfeeding. The breasts continue growing during pregnancy due to estrogen and progesterone.


During menopause, the ovaries stop producing hormones that support your breasts, including oestrogen and progesterone, so they start to lose fat and subcutaneous tissues. If you are not on hormone replacement therapy (HRT), the natural loss of these hormones causes your breasts to become smaller than they were before menopause.

Breasts naturally lose some of their fat during the aging process, causing them to sag more. Gravity naturally pulls this heavier tissue towards the ground, causing the breasts to sag over time.

Breasts are made up of glandular, fatty, and connective tissues. Most of the changes that occur during puberty are due to growth in the glandular tissues, which eventually slows down as you approach menopause. The fatty tissue surrounding your breasts will change throughout your entire life but is not affected by hormonal changes. Fatty tissues give the breasts their shape, colour, and fullness. Because the glandular tissue continues to grow during puberty, this is one of the reasons that adolescent girls may experience some breast growth before puberty begins. The ligaments around your breasts are what hold them up, but they are not affected by hormones or puberty.

Connective tissue and ligaments hold the breasts up and keep them close to your chest, which gives them their round shape. Some women have looser or less supportive ligaments than others because of age, genetics, pregnancy, breastfeeding, weight changes, etc., which can cause their breasts to become saggy over time.

The skin around your breasts provides the nipple and areola with its pigmentation. As you age, the natural loss of collagen in these tissues causes stretch marks to become more visible on your breasts. Breasts may also appear wrinkled when the development of elastin, an elastic-type protein in connective tissue that gives youthful skin its bounce, declines with age.

So as you age your breasts change substantially. Don't be concerned and make sure you are always checking for signs of breast cancer using the self checking process

How to self check your breast for signs of breast cancer

You should perform this process each month, but especially if you are due for your regular breast examination.

Lying down with a pillow under your right shoulder, use the pads of your three middle fingers of both hands to feel for lumps or thickening in your breasts. Avoid using the tips of your fingers because they may be more sensitive and you may miss something.

Cup each of your breasts with the opposite hand, applying gentle pressure to compress tissue evenly, and feel for lumps or thickening.

Is there any pain associated with the lump you found? If so, where is the pain located—is it a sharp, dull, burning or throbbing pain? Don't be afraid to probe the lump with your fingers to see if it changes in any way.

Cup each of your breasts again, this time using stronger pressure as you compress the tissue from the outside and move towards the nipple. If you feel a hard area as you press on different parts of your breasts, that is usually a sign that there may be a solid lump inside.

Is there any dimpling in the skin of your breasts? Dimples usually indicate an accumulation of fat underneath the surface. However, very rarely they can also be caused by fluid-filled cysts or tumours.

Finally, pressing firmly with your fingers, slide them around the edge of each breast, feeling for any unusual lumps or bumps.

If you feel anything that causes your fingers to linger longer than the rest, such as a hard lump, or if there is pain associated with it, make an appointment to see your doctor right away.

Every month perform this process and keep track of what you find in case something changes over time.