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Breast Size, Appearance, and Changes Over Time
The size and shape of women’s breasts varies considerably. Some women have a large
amount of breast tissue, and therefore, have large breasts. Other women have a smaller
amount of tissue with little breast fat.
Factors that may influence a woman’s breast size include:
- Volume of breast tissue
- Family history
- Age
- Weight loss or gain
- History of pregnancies and lactation
- Thickness and elasticity of the breast skin
- Degree of hormonal influences on the breast (particularly estrogen and progesterone)
- Menopause
A woman’s breasts are rarely balanced (symmetrical). Usually, one breast is
slightly larger or smaller, higher or lower, or shaped differently than the other. The
size and characteristics of the nipple also vary greater from one woman to another. In
some women, the nipples are constantly erect. In others, they will only become erect when
stimulated by cold or touch. Some women also have inverted (turned in) nipples. Inverted
nipples are not a cause for concern unless the condition is a new change. Since there are
hair follicles around the nipple, hair on the breast is not uncommon.
The nipple can be flat, round, or cylindrical in shape. The color of the nipple is
determined by the thinness and pigmentation of its skin. The nipple and areola (pigmented
region surrounding the nipple) contain specialized muscle fibers that respond to
stimulation to make the nipple erect. The areola also houses the Montgomery’s gland
that may appear as tiny, raised bumps on the surface of the areola. The Montgomery’s
gland helps lubricate the areola. When the nipple is stimulated, the muscle fibers will
contract, the areola will pucker, and the nipples become hard.
Breast shape and appearance undergo a number of changes as a woman ages. In young
women, the breast skin stretches and expands as the breasts grow, creating a rounded
appearance. Young women tend to have denser breasts (more glandular tissue) than older
women.
On mammogram films, breast masses, including both
non-cancerous and cancerous lesions, appear as white regions. Fat appears as black regions
on the films. All other components of the breast (glands, connective tissue, tumors,
calcium deposits, etc.) appear as shades of white on a mammogram. In general, the younger
the woman, the denser her breasts. As a woman ages, her breasts become less dense and the
space is filled with fatty tissue shown as dark areas on mammography x-rays. It is usually
easier for radiologists to detect breast cancer in older women because abnormal areas are
easier to spot.
During each menstrual cycle, breast tissue tends to swell from changes in the
body’s levels of estrogen and progesterone. The milk glands and ducts enlarge, and in
turn, the breasts retain water. During menstruation, breasts may temporarily feel swollen,
painful, tender, or lumpy. Physicians recommend that women practice monthly breast self-exams the week following menstruation when the breasts are
least tender.
Fibrocystic breast condition is a common
benign (non-cancerous) breast condition related to the menstrual cycle. Some women with
fibrocystic breasts experience cysts (accumulated packets of fluid), lumpiness, areas of
thickening, tenderness, or breast pain. Symptoms of fibrocystic change will usually
subside after menopause but may be prolonged if a woman uses hormone
replacement therapy.
Breast Changes During Pregnancy
Women should continue monthly breast self-exams during pregnancy.
It is especially important that a clinical breast exam be performed by the physician or
nurse during the first doctor’s appointment of the pregnancy, before the breasts go
through significant physiologic changes. Clinical breast exams should
then continue on a monthly basis during pregnancy. Screening
mammograms in asymptomatic women (women who have no symptoms of breast cancer) are not
performed during pregnancy or lactation and may be performed at a later time.
During pregnancy, a variety of breast changes occur. Typically, breasts become tender
and the nipples become sore a few weeks after conception. The breasts also increase in
size very quickly. It is not uncommon for a woman’s breasts to increase by one or two
cup sizes during and after pregnancy. The most rapid period of breast growth is during the
first eight weeks of pregnancy. The Montgomery’s gland surrounding the areola
(pigmented region surrounding the nipple) becomes darker and more prominent, and the
areola itself darkens. The nipples also become larger and more erect as they prepare for
milk production. The blood vessels within the breast enlarge as surges of estrogen
stimulate the growth of the ducts and surges of progesterone cause the glandular tissue to
expand.
Two hormones are responsible for milk production: prolactin and oxytocin. Prolactin is
sometimes referred to as the "mothering hormone" because some people believe it
also causes a tranquilizing effect that makes women feel more maternal. The body begins
producing prolactin approximately eight weeks after conception. As the pregnancy
progresses, the levels of prolactin steadily increase, peaking when the woman gives birth.
As the body produces more and more prolactin, high levels of estrogen and progesterone
block some of the prolactin receptors and inhibit milk production until after the baby is
born.
After birth, estrogen and progesterone levels decrease and the production of prolactin
declines. The breasts will usually begin to produce milk three to five days after a woman
has given birth. During these few days before milk is produced, the body produces
colostrum, a liquid substance that contains antibodies to help protect the infant against
infections. Some physicians believe that colostrum also decreases an infant's chances of
developing asthma and other allergies. Within a few days, the infant's own immune system
will develop and he or she will not need colostrum.
The other hormone responsible for milk production, oxytocin, delivers the milk that
prolactin has produced. When an infant suckles at the mother’s breast, it brings milk
out of the nipples. This suction signals the body to make more milk (using prolactin) and
deliver more milk (using oxytocin). The body also produces a variety of other hormones
(insulin, thyroid, cortisol) that provide the infant with nutrition when he or she takes
the mother’s milk. A woman’s body will continue to produce milk until she stops breast-feeding, and even then, it may take several months for
milk production to completely stop. The breasts will usually return to their previous size
(or slightly smaller) after breast-feeding is completed.
Breast Changes After Menopause
When a woman reaches menopause (typically in her late 40s or early 50s), her body stops
producing estrogen and progesterone. The loss of these hormones causes a variety of
symptoms in many women including hot flashes, night sweats, mood changes, vaginal dryness
and difficulty sleeping. During this time, the breasts also undergo change. For some
women, the breasts become more tender and lumpy, sometimes forming cysts (accumulated
packets of fluid).
The breasts’ glandular tissue, which has been kept firm so that the glands could
produce milk, shrinks after menopause and is replaced with fatty tissue. The breasts also
tend to increase in size and sag because the fibrous (connective) tissue loses its
strength. Because the breasts become less dense after menopause, it is often easier for
radiologists to detect breast cancer on an older woman’s mammogram films, since
abnormalities are not hidden by breast density. Since a woman’s risk of breast cancer
increases with age, all women should begin receiving annual screening mammograms at age 40, and continue monthly breast self-exams
and physician-performed clinical breast exams every year. Click here to
learn more about breast cancer.
Additional Resources and References
Updated: March 18, 2008
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