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Breast Cancer and Pregnancy

Most lumps, nipple discharges, and other worrisome breast changes discovered during pregnancy are not cancerous. Breast abnormalities during pregnancy can be caused by many of the same processes seen in non-pregnant women or from benign changes to the breast tissue that occur during pregnancy and lactation (breast-feeding). However, breast cancer can occur during pregnancy and is actually diagnosed more frequently in pregnant women than in non-pregnant women of the same age. Breast cancer occurs in one in 3,000 (0.03%) to one in 10,000 (0.01%) of all pregnant women. Breast cancer during pregnancy is diagnosed in greater numbers in women who delay childbearing until their later 30s or early 40s. This is due primarily to the fact that the risk of breast cancer increases with age.

    Breast Changes During Pregnancy and Lactation (Breast-Feeding)

    During pregnancy, increased levels of the hormones estrogen and progesterone stimulate a variety of breast changes. Typically, the breasts become tender and the nipples become sore a few weeks after conception. The Montgomery’s gland surrounding the areola (the pigmented region around the nipple) becomes darker and more prominent, and the areola itself darkens.

    One of the most common changes stimulated by the hormones of pregnancy is a rapid period of breast growth, especially during the first eight weeks of pregnancy. In fact, it is not uncommon for a woman’s breasts to increase by one or two cup sizes during pregnancy and lactation. This rapid growth is due to anatomic changes in the breast tissue that include expansion of the blood vessels and fluid retention within the breasts. In addition, estrogens stimulate the growth of the breast ducts and surges of progesterone cause the glandular tissue to expand.

    It is not uncommon for the breasts to increase by one to two bra cup sizes during and pregnancy and lactation. The breasts usually return to their previous size, or slightly smaller, after breast-feeding is completed.

    Later in the first trimester of pregnancy, levels of the two hormones responsible for milk production, prolactin and oxytocin, begin to increase. 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 breasts secrete 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 need for high levels of the maternal antibodies in the colostrum decreases. At about the same time, the breasts begin to produce milk, which contains lower levels of antibodies that are passed on to the infant during breast-feeding. These antibodies are believed to decrease the infant’s susceptibility to disease and infections in early life.

    The other hormone responsible for milk production, oxytocin, triggers the delivery of milk that prolactin has produced. When an infant suckles at the mother’s breast, milk is actively drawn out of the nipples by the suckling action and passively delivered to the infant by the contraction of small muscles surrounding the ducts in the breast. This process is commonly called the let-down reflex. The infant’s suction signals the body to produce more milk (using prolactin) and deliver more milk (using oxytocin). A variety of other hormones that stimulate growth and development in the infant are also delivered in the breast milk, including insulin, thyroid, and cortisol.

    A woman’s body continues to produce milk until she stops breast-feeding or mechanically pumping breast milk. Even then, it may take several months for milk production to completely stop. The breasts usually return to their previous size, or slightly smaller, after breast-feeding is completed.

    Breast Health Guidelines During Pregnancy

    A woman should continue practicing monthly breast self-exams during pregnancy at about seven to 10 days after her normal period would have occurred. 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. Some changes or lumps are more difficult to evaluate once the breasts have enlarged and have become more nodular. Clinical breast exams should continue on a monthly basis during pregnancy.

    A main concern with breast cancer during pregnancy is a delay in the detection of a breast abnormality. The changes that occur during pregnancy may make cancers more difficult to diagnose and may result in a woman being diagnosed with breast cancer at a more advanced stage, when the chances of successful treatment and survival are lower. Vigilant monthly breast self-exams and clinical breast exams during pregnancy and lactation (breast-feeding) can help prevent the delayed diagnosis of breast cancer and enable optimal treatment.

    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. However, if a breast abnormality (such as a strange lump) is detected during pregnancy, a diagnostic mammogram and/or ultrasound (sonogram) may be performed. A diagnostic mammogram involves taking x-rays of the breast from special angles and/or using special magnification. Mammography uses a very low dose of radiation and is considered safe for the fetus if there is a medical need for the exam. A lead apron is usually placed over the woman’s stomach/abdomen area during the mammogram to shield the developing fetus.

    Vigilant monthly breast self-exams and clinical breast exams during pregnancy and lactation (breast-feeding) can help prevent the delayed diagnosis of breast cancer and enable optimal treatment.

    Evaluating a Breast Abnormality During Pregnancy

    The hormonal changes during pregnancy and lactation (breast-feeding) may influence the growth of estrogen-sensitive tumors. Non-cancerous tumors are common during pregnancy and their growth may be stimulated by increased hormone levels. However, all breast lumps and abnormalities should be evaluated by a physician to distinguish between the more common benign changes and the potentially malignant (cancerous) ones.

    Non-cancerous conditions that are common during pregnancy include:

    • Cysts (collections of fluid)
    • Galactoceles (milk-filled cysts)
    • Fibroadenomas (tumors; existing ones may enlarge during pregnancy)

    It is fairly common for the nipples to discharge small amounts of milky, clear, or sometimes bloody fluid during pregnancy and lactation. During pregnancy and lactation, breast tissue grows rapidly. Rapid tissue growth can lead to irritation of the breast ducts, causing nipple discharge. This discharge, whether blood or other fluid, is usually related to a non-cancerous condition, such as shedding of the cells lining the breast ducts or a papilloma (a benign wart-like growth). However, patients should consult their physicians if they experience nipple discharge to determine whether the discharge requires further examination.

    If a breast abnormality or lump is detected during pregnancy, it should be presented immediately to a physician who will conduct a thorough clinical breast exam. The physician may also order an ultrasound (sonogram) exam and/or mammogram. Ultrasound is excellent at distinguishing cysts and is routinely used for fetal imaging because it does not harm the fetus. Mammography, with proper shielding, is also considered safe for a pregnant woman and her fetus. Mammography uses a very low level of radiation and should not be delayed if deemed necessary.

    In many cases, a non-surgical biopsy will be performed if a suspicious breast lump or abnormality is detected in a pregnant woman. A biopsy helps determine whether a breast mass is cancerous or benign. Fine needle aspiration biopsy (FNA) involves using a thin needle to drain fluid or sample cells from the breast. FNA is often used to identify and drain cysts or remove cells for microscopic examination. Other methods of breast biopsy that use larger needles than FNA, such as core needle biopsy or vacuum-assisted biopsy, can also be performed safely during pregnancy if they are warranted. In some cases, an open surgical biopsy may be necessary to diagnose a breast mass. If so, careful planning can help reduce any risks to the mother and fetus.

    Evaluating a Breast Abnormality During Lactation (Breast-Feeding)

    If a worrisome breast lump or abnormality is found after birth when a woman is breast-feeding, diagnostic mammography and/or other breast imaging exams should not be delayed. Mammography is considered safe and can be accurate for women who are breast-feeding when performed with care. Some suggest that the breast should be completely emptied of milk immediately before the mammogram, either via nursing or breast pump. This decreases the density through which the x-rays must penetrate and helps improve image quality.

    It is important to keep in mind that imaging tests are not foolproof and may not detect a mass even when it can be felt during a physical examination. Approximately 10% to 15% of breast masses are missed with mammography or ultrasound (sonography) in women who are not lactating, and this percentage can be as high as 25% in the denser, larger, lactating breast. For this reason, a breast abnormality detected during lactation will often need to be biopsied to determine whether it is cancerous or benign.

    Fine needle aspiration (FNA) involves using a thin needle to sample fluid or cells from the breast. FNA is often used to identify or drain cysts (collections of fluid). Other biopsy methods, such as core needle biopsy or open surgical biopsy, can also be performed safely. However, these more invasive methods are usually reserved for cases when the diagnosis cannot be made by other, less invasive means. This is because milk fistulas (abnormal passages of milk) or collections of milk in the breast may result when a biopsy is performed on a lactating breast. Nevertheless, milk fistulas are rarely a problem and are more of an inconvenience compared with the more dangerous possibility of an undiagnosed breast cancer. If a biopsy is performed and a collection of milk does result, it can easily be drained by fine needle aspiration in the physician’s office.

    Most of the breast problems encountered during breast-feeding are inflammatory or infectious complications rather than breast cancer. Nasopharyngeal organisms (such as a cold virus) from the infant’s mouth, sinuses, and other air passages can be a common source of infection in breast-feeding women.

    Common breast-feeding problems include:

    • Inadequate milk supply
    • Blocked milk duct
    • Breast engorgement
    • Breast mastitis (infection)
    • Nipple discharge
    • Nipple confusion
    • Breast pain
    • Nipple soreness
    • Inverted or flat nipples

      Click here for more information about these problems and how they can be treated. 

    A Breast Cancer Diagnosis During Pregnancy

    While a diagnosis of breast cancer during pregnancy can be quite distressful, it is not necessary to terminate the pregnancy unless the woman chooses. A woman’s chances of surviving breast cancer are the same regardless of whether the pregnancy is terminated or not, although more treatment options may be available if the pregnancy is ended. The occurrence of breast cancer itself during pregnancy does not appear to harm the fetus. However, some of the tests and treatments may increase the risk of malformation or miscarriage of the fetus; the risk varies depending on the stage (trimester) of the pregnancy.

    It is not necessary to terminate the pregnancy if breast cancer is diagnosed.

    If a pregnant woman is diagnosed with breast cancer, her team of cancer specialists will first need to determine the stage of the cancer. Staging breast cancer includes accurately measuring the size of the tumor and the extent to which it may have spread within the breast and/or to other locations. In addition to imaging exams such as ultrasound (sonograms), blood tests will typically be performed to determine whether the cancer has spread to other organs in the body (such as the bone, liver, or lung). In some cases, physicians may test for breast cancer markers, such as CEA or CA 15-3, which may be elevated in women with breast cancer. However, blood markers may be less accurate in early-stage breast cancers or in pregnant women and may not be helpful. While chest x-rays are performed during pregnancy to determine whether the cancer has spread to the lungs and other areas, certain tests such as CT scans are not typically performed on pregnant women because of their higher radiation exposure.

    The treatment of breast cancer during pregnancy should not be delayed unless a woman is within 2 to 3 weeks from her delivery date. Radiation, chemotherapy, and drug therapy are not typically given during pregnancy because they can potentially harm the fetus. However, recent studies show that women who receive chemotherapy during the second or third trimesters of pregnancy (after the first three months) still have good chances of having healthy babies. In more than one study, women who received chemotherapy during the second or third trimesters of pregnancy had live births and only a few had complications from the chemotherapy, such as early labor and low birth weight. However, the long-term effects of exposure to chemotherapy drugs during pregnancy are less well-studied and should be discussed in detail with treating physicians.

    Surgery is commonly performed during pregnancy for a variety of conditions, and if proper care is taken during anesthesia and after surgery, generally no harm comes to the fetus. Typically, a mastectomy is recommended if breast cancer is diagnosed during the first or second trimester of pregnancy (the first six months). Mastectomy involves surgically removing the entire breast and often some or all of the axillary (underarm) lymph nodes. Mastectomy often prevents the need for radiation treatment. Chemotherapy or drug therapy is typically delayed until later in the pregnancy or after delivery, although the risks and benefits must be carefully weighted.

    If breast cancer is diagnosed during the third trimester of pregnancy (the final three months), either mastectomy or breast-conserving therapy (i.e., lumpectomy) with lymph node removal may be performed as needed. Lumpectomy involves only removing the cancerous tumor and a surrounding margin of normal breast tissue. Radiation, chemotherapy, or drug therapy is usually delayed until after childbirth. Women who receive chemotherapy or other drug therapies after childbirth should not breast-feed because the drugs could be passed through the breast milk. Breast reconstruction is not typically performed until after childbirth and lactation, when the breasts return to their normal size and milk production has ceased completely.

    Pregnancy After Breast Cancer

    A number of women who have successfully undergone treatment for breast cancer wish to have further pregnancies. Stage for stage, breast cancer during pregnancy has a similar prognosis (outcome) to that of breast cancer in young, non-pregnant women. According to recent studies, women who have been successfully treated for breast cancer in the past do not usually experience fertility problems unless chemotherapy is administered as part of the treatment. Pre-menopausal women treated with chemotherapy should be aware that the treatment can cause infertility and/or premature menopause, especially in older pre-menopausal woman (typically in their forties) who are already naturally less fertile and closer to menopause. The hormonal and metabolic changes that occur during pregnancy do not typically pose any increased risk of recurrent breast cancer, although studies in this area continue.

    One study led by Dr. Priscilla Velentgas of the University of Seattle found that women who became pregnant after being diagnosed with Stage I or Stage II invasive breast cancer were not at greater risk of recurrent breast cancer than survivors that did not become pregnant. Further research has since confirmed the study. Additionally, neither the number of pregnancies nor the time lapsed between treatment for breast cancer and pregnancy appear to have any noticeable effect on long-term breast cancer prognosis.

    For women diagnosed with early-stage breast cancer, pregnancy is usually reasonable two or more years after diagnosis and treatment. However, some women may be advised to have children sooner if they are older and there are other considerations. Several details such as cancer type, degree of metastasis (spread), and amount of radiation and/or chemotherapy received should be considered before advising a woman whether it is safe to become pregnant after breast cancer. For example, those at higher risk for an early recurrence may be advised to wait and be closely observed prior to attempting a pregnancy. If a pregnancy is successful after having been treated for breast cancer, some women who have had radiation therapy on one breast find that a sufficient amount of milk for breast-feeding cannot be produced by the irradiated (treated) breast. However, the other, normal breast can often produce enough milk to enable breast-feeding.

    Women with Stage IV (metastatic) breast cancer or recurrent tumors may not be good candidates for future pregnancies. Chemotherapy may also have an adverse effect on the ovaries and lead to fertility problems or a higher rate of spontaneous miscarriages. However, each individual is different, and all pre-menopausal women should discuss the issue of future pregnancies with their physicians before their initial breast cancer treatment if they are interested in having children after treatment. In some cases, women may wish to consider banking eggs prior to treatment (particularly chemotherapy) if they wish to have children in the future.

    Additional Resources and References

    Updated: September 2010