Breastfeed your baby

Tip #9 Breastfeed your baby

Breast-feed to reduce cancer risk – Overview

•There is unequivocal evidence that breastfeeding protects against a variety of diseases and conditions in infants.
•Breast-feeding protects infants against lymphoma, leukemia, and Hodgkins disease
•There are also maternal health benefits to breastfeeding such as decreased risk of breast and ovarian cancers.
•Breast-feeding decreased postpartum bleeding and more rapid uterine involution.
•In a study, the longer women had breastfed during their lifetime, the less likely they were to get breast cancer.
•Research now looking into whether breastfeeding can help to protect women with faulty genes – BRCA1 and BRCA2.

Benefits of Breast Feeding

Source: American Academy of Pediatrics (AAP)

Most health professionals are familiar with the benefits of breastfeeding. The AAP continues to support the unequivocal evidence that breastfeeding protects against a variety of diseases and conditions in the infant such as:

  • bacteremia
  • diarrhea
  • respiratory tract infection
  • necrotizing enterocolitis
  • otitis media
  • urinary tract infection
  • late-onset sepsis in preterm infants
  • type 1 and type 2 diabetes
  • lymphoma, leukemia, and Hodgkins disease
  • childhood overweight and obesity

There are also maternal health benefits to breastfeeding such as:

  • decreased postpartum bleeding and more rapid uterine involution
  • decreased menstrual blood loss and increased child spacing (lactational amenorrhea)
  • earlier return to prepregnancy weight
  • decreased risk of breast and ovarian cancers

Breastfeeding is also a great benefit to the environment and society. Breastfeeding families are sick less often and the parents miss less work. It does not require the use of energy for manufacturing or create waste or air pollution. There is no risk of contamination and it is always at the right temperature and ready to feed.

Breastfeeding and Cancer

Source: American Institute for Cancer Research
Many know that breastfeeding gives babies a healthy start in life. It provides the nutrients babies need, helps protect them from infections and asthma and boosts their immune system.

But relatively few know that breastfeeding protects both mother and child against cancer.

But that finding is why AICR recommends that new mothers breastfeed exclusively for up to six months and then add other liquids and foods. This advice is in line with recommendations from the World Health Organization.

How is breastfeeding linked to cancer prevention?

There is convincing evidence that breastfeeding reduces the risk of breast cancer in mothers and probably helps prevent excess weight gain in their children.

What are the long-term benefits for the baby?

Breastfed babies have a decreased risk of becoming overweight or obese as they grow. Research shows that babies who are breastfed are less likely to consume too many calories than babies who are fed infant formula.

It is now well known that obesity is a strong risk factor for many cancers, including those of the colon and breast in postmenopausal women).

What are the long-term benefits for the mother?

As well as helping mothers lose any excess baby weight more quickly, breastfeeding can reduce the risk of breast cancer.

The protective effect of breastfeeding is likely due to the balance of hormones produced during the breastfeeding process. By lowering levels of some cancer-related hormones in the mother’s body, risk of cancer is reduced.

Also, at the end of breastfeeding, the body gets rid of many cells in the breast, some of which may have DNA damage. This reduces the risk of developing breast cancer in the future.

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Source: The website of the National Cancer Institute (

Is there a relationship between pregnancy and breast cancer risk?

Studies have shown that a woman’s risk of developing breast cancer is related to her exposure to hormones that are produced by her ovaries (endogenous estrogen and progesterone). Reproductive factors that increase the duration and/or levels of exposure to ovarian hormones, which stimulate cell growth, have been associated with an increase in breast cancer risk. These factors include early onset of menstruation, late onset of menopause, and factors that may allow breast tissue to be exposed to high levels of hormones for longer periods of time, such as later age at first pregnancy and never having given birth.

Conversely, pregnancy and breastfeeding, which both reduce a woman’s lifetime number of menstrual cycles, and thus her cumulative exposure to endogenous hormones (1), are associated with a decrease in breast cancer risk. In addition, pregnancy and breastfeeding have direct effects on breast cells, causing them to differentiate, or mature, so they can produce milk. Some researchers hypothesize that these differentiated cells are more resistant to becoming transformed into cancer cells than cells that have not undergone differentiation (2, 3).

Are any pregnancy-related factors associated with a lower risk of breast cancer?

Some pregnancy-related factors have been associated with a reduced risk of developing breast cancer later in life. These factors include:

  • Early age at first full-term pregnancy. Women who have their first full-term pregnancy at an early age have a decreased risk of developing breast cancer later in life. For example, in women who have a first full-term pregnancy before age 20, the risk of developing breast cancer is about half that of women whose first full-term pregnancy occurs after the age of 30 (4). This risk reduction is limited to hormone receptor–positive breast cancer; age at first full-term pregnancy does not appear to affect the risk of hormone receptor-negative breast cancer (5, 6).
  • Increasing number of births. The risk of breast cancer declines with the number of children borne. Women who have given birth to five or more children have half the breast cancer risk of women who have not given birth (7). Some evidence indicates that the reduced risk associated with a higher number of births may be limited to hormone receptor–positive breast cancer.
  • History of preeclampsia. Women who have had preeclampsia may have a decreased risk of developing breast cancer (8–11). Preeclampsia is a complication of pregnancy in which a woman develops high blood pressure and excess amounts of protein in her urine. Scientists are studying whether certain hormones and proteins associated with preeclampsia may affect breast cancer risk (8, 12, 13).
  • Longer duration of breastfeeding. Breastfeeding for an extended period (at least a year) is associated with decreased risks of both hormone receptor–positive and hormone receptor–negative breast cancers (6, 14).

Are any pregnancy-related factors associated with an increase in breast cancer risk?

Some factors related to pregnancy may increase the risk of breast cancer. These factors include:

  • Older age at birth of first child. The older a woman is when she has her first full-term pregnancy, the higher her risk of breast cancer. Women who are older than 30 when they give birth to their first child have a higher risk of breast cancer than women who have never given birth (15).
  • Recent childbirth. Women who have recently given birth have a short-term increase in breast cancer risk that declines after about 10 years. The reason for this temporary increase is not known, but some researchers believe that it may be due to the effect of high levels of hormones on the development of cancers or to the rapid growth of breast cells during pregnancy (16).
  • Taking diethylstilbestrol (DES) during pregnancy. DES is a synthetic form of estrogen that was used between the early 1940s and 1971 to prevent miscarriages and other pregnancy problems. Women who took DES during pregnancy may have a slightly higher risk of developing breast cancer than women who did not take DES during pregnancy (17). Some studies have shown that daughters of women who took DES during pregnancy may also have a slightly higher risk of developing breast cancer after age 40 than women who were not exposed to DES while in the womb (18), but the evidence is inconsistent (19).

Is abortion linked to breast cancer risk?

A few retrospective (case-control) studies reported in the mid-1990s suggested that induced abortion (the deliberate ending of a pregnancy) was associated with an increased risk of breast cancer. However, these studies had important design limitations that could have affected the results. A key limitation was their reliance on self-reporting of medical history information by the study participants, which can introduce bias. Prospective studies, which are more rigorous in design and unaffected by such bias, have consistently shown no association between induced abortion and breast cancer risk (20–25). Moreover, in 2009, the Committee on Gynecologic Practice of the American College of Obstetricians and Gynecologists concluded that “more rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk” (26). Major findings from these studies include:

  • Women who have had an induced abortion have the same risk of breast cancer as other women.
  • Women who have had a spontaneous abortion (miscarriage) have the same risk of breast cancer as other women.
  • Cancers other than breast cancer also appear to be unrelated to a history of induced or spontaneous abortion.

Does pregnancy affect the risk of other cancers?

Research has shown the following with regard to pregnancy and the risk of other cancers:

  • Women who have had a full-term pregnancy have reduced risks of ovarian (27, 28) and endometrial (29) cancers. Furthermore, the risks of these cancers decline with each additional full-term pregnancy.
  • Pregnancy also plays a role in an extremely rare type of tumor called a gestational trophoblastic tumor. In this type of tumor, which starts in the uterus, cancer cells grow in the tissues that are formed following conception.
  • There is some evidence that pregnancy-related factors may affect the risk of other cancer types, but these relationships have not been as well studied as those for breast and gynecologic cancers. The associations require further study to clarify the exact relationships.

As in the development of breast cancer, exposures to hormones are thought to explain the role of pregnancy in the development of ovarian, endometrial, and other cancers. Changes in the levels of hormones during pregnancy may contribute to the variation in risk of these tumors after pregnancy (30).

Does fertility treatment affect the risk of breast or other cancers?

Women who have difficulty becoming pregnant or carrying a pregnancy to term may receive fertility treatment. Such treatment can include surgery (to repair diseased, damaged, or blocked fallopian tubes or to remove uterine fibroids, patches of endometriosis, or adhesions); medications to stimulate ovulation; and assisted reproductive technology.

Ovarian stimulation and some assisted reproductive technologies involve treatments that temporarily change the levels of estrogen and progesterone in a woman’s body. For example, women undergoing in vitro fertilization (IVF) receive multiple rounds of hormone treatment to first suppress ovulation until the developing eggs are ready, then stimulate development of multiple eggs, and finally promote maturation of the eggs. The use of hormones in some fertility treatments has raised concerns about possible increased risks of cancer, particularly cancers that are linked to elevated levels of these hormones.

Many studies have examined possible associations between use of fertility drugs or IVF and the risks of breast, ovarian, and endometrial cancers. The results of such studies can be hard to interpret because infertility itself is linked to increased risks of these cancers (that is, compared with fertile women, infertile women are at higher risk of these cancers even if they do not use fertility drugs). Also, these cancers are relatively rare and tend to develop years after treatment for infertility, which can make it difficult to link their occurrence to past use of fertility drugs.

  • Breast cancer: The bulk of the evidence is consistent with no increased risk of breast cancer associated with the use of fertility drugs or IVF (31–34). 
  • Ovarian cancer: There is some uncertainty about whether treatment for infertility is a risk factor for ovarian cancer. A 2013 systematic review of 25 studies that included more than 180,000 women found, overall, no strong evidence of an increased risk of invasive ovarian cancer for women treated with fertility drugs (35). In one study, women who underwent IVF had an increase in risk of ovarian borderline malignant tumors (36).
  • Endometrial cancer: Overall, the use of fertility drugs or IVF does not appear to increase the risk of endometrial cancer (34).

Selected References

  1. Colditz GA, Baer HJ, Tamimi RM. Breast cancer. In: Schottenfeld D, Fraumeni JF, editors. Cancer Epidemiology and Prevention. 3rd ed. New York: Oxford University Press, 2006.
  2. Russo J, Moral R, Balogh GA, Mailo D, Russo IH. The protective role of pregnancy in breast cancer. Breast Cancer Research 2005; 7(3):131–142. [PubMed Abstract]
  3. Britt K, Ashworth A, Smalley M. Pregnancy and the risk of breast cancer. Endocrine-Related Cancer 2007; 14(4):907–933. [PubMed Abstract]
  4. Bernstein L. Epidemiology of endocrine-related risk factors for breast cancer. Journal of Mammary Gland Biology and Neoplasia 2002; 7(1):3–15. [PubMed Abstract]
  5. Lord SJ, Bernstein L, Johnson KA, et al. Breast cancer risk and hormone receptor status in older women by parity, age of first birth, and breastfeeding: a case-control study. Cancer Epidemiology, Biomarkers & Prevention 2008; 17(7):1723–1730. [PubMed Abstract]
  6. Ma H, Bernstein L, Pike MC, Ursin G. Reproductive factors and breast cancer risk according to joint estrogen and progesterone receptor status: a meta-analysis of epidemiological studies. Breast Cancer Research 2006; 8(4):R43. [PubMed Abstract]
  7. Lambe M, Hsieh CC, Chan HW, et al. Parity, age at first and last birth, and risk of breast cancer: a population-based study in Sweden. Breast Cancer Research and Treatment 1996; 38(3):305–311.[PubMed Abstract]
  8. Vatten LJ, Romundstad PR, Ødegård RA, et al. Alpha-foetoprotein in umbilical cord in relation to severe pre-eclampsia, birth weight and future breast cancer risk. British Journal of Cancer 2002; 86(5):728–731.[PubMed Abstract]
  9. Terry MB, Perrin M, Salafia CM, et al. Preeclampsia, pregnancy-related hypertension, and breast cancer risk. American Journal of Epidemiology 2007; 165(9):1007–1014.[PubMed Abstract]
  10. Nechuta S, Paneth N, Velie EM. Pregnancy characteristics and maternal breast cancer risk: a review of the epidemiologic literature. Cancer Causes and Control 2010; 21(7):967–989.[PubMed Abstract]
  11. Opdahl S, Romundstad PR, Alsaker MD, Vatten LJ. Hypertensive diseases in pregnancy and breast cancer risk. British Journal of Cancer 2012; 107(1):176-182.[PubMed Abstract]
  12. Tamimi R, Lagiou P, Vatten LJ, et al. Pregnancy hormones, pre-eclampsia, and implications for breast cancer risk in the offspring. Cancer Epidemiology, Biomarkers, and Prevention 2003; 12(7):647–650.[PubMed Abstract]
  13. Vatten LJ, Romundstad PR, Trichopoulos D, Skjærven R. Pre-eclampsia in pregnancy and subsequent risk for breast cancer. British Journal of Cancer 2002; 87(9):971–973.[PubMed Abstract]
  14. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50,302 women with breast cancer and 96,973 women without the disease. The Lancet 2002; 360(9328):187–195.[PubMed Abstract]
  15. Kelsey JL, Gammon MD, John EM. Reproductive factors and breast cancer. Epidemiologic Reviews 1993; 15(1):36–47.[PubMed Abstract]
  16. Dickson RB, Pestell RG, Lippman ME. Cancer of the breast. In: DeVita VT Jr., Hellman S, Rosenberg SA, editors. Cancer: Principles and Practice of Oncology. Vol. 1 and 2. 7th ed. Philadelphia: Lippincott Williams and Wilkins, 2004.
  17. Titus-Ernstoff L, Hatch EE, Hoover RN, et al. Long-term cancer risk in women given diethylstilbestrol (DES) during pregnancy. British Journal of Cancer 2001; 84(1):126–133.[PubMed Abstract]
  18. Hoover RN, Hyer M, Pfeiffer RM, et al. Adverse health outcomes in women exposed in utero to diethylstilbestrol. New England Journal of Medicine 2011; 365(14):1304-14.[PubMed Abstract]
  19. Verloop J, van Leeuwen FE, Helmerhorst TJ, van Boven HH, Rookus MA. Cancer risk in DES daughters. Cancer Causes & Control 2010; 21(7):999-1007.[PubMed Abstract]
  20. Reeves GK, Kan SW, Key T, et al. Breast cancer risk in relation to abortion: results from the EPIC study. International Journal of Cancer 2006; 119(7):1741–1745.[PubMed Abstract]
  21. Michels KB, Xue F, Colditz GA, Willett WC. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Archives of Internal Medicine 2007; 167(8):814–820.[PubMed Abstract]
  22. Beral V, Bull D, Doll R, Peto R, Reeves G. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83,000 women with breast cancer from 16 countries. Lancet 2004; 363(9414):1007–1016.[PubMed Abstract]
  23. Henderson KD, Sullivan-Halley J, Reynolds P, et al. Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study. Contraception 2008; 77(6):391–396.[PubMed Abstract]
  24. Lash TL, Fink AK. Null association between pregnancy termination and breast cancer in a registry-based study of parous women. International Journal of Cancer 2004; 110(3):443–448.[PubMed Abstract]
  25. Rosenblatt KA, Gao DL, Ray RM, et al. Induced abortions and the risk of all cancers combined and site-specific cancers in Shanghai. Cancer Causes and Control 2006; 17(10):1275–1280.[PubMed Abstract]
  26. Committee on Gynecologic Practice. ACOG Committee Opinion No. 434: induced abortion and breast cancer risk. Obstetrics and Gynecology 2009; 113(6):1417–1418.[PubMed Abstract]
  27. Hankinson SE, Colditz GA, Hunter DJ, et al. A prospective study of reproductive factors and risk of epithelial ovarian cancer. Cancer 1995; 76(2):284–290.[PubMed Abstract]
  28. La Vecchia C, Negri E, Franceschi S, Parazzini F. Long-term impact of reproductive factors on cancer risk. International Journal of Cancer 1993; 53(2):215–219.[PubMed Abstract]
  29. Titus-Ernstoff L, Perez K, Cramer DW, et al. Menstrual and reproductive factors in relation to ovarian cancer risk. British Journal of Cancer 2001; 84(5):714–721.[PubMed Abstract]
  30. Persson I. Estrogens in the causation of breast, endometrial and ovarian cancers―evidence and hypotheses from epidemiological findings. Journal of Steroid Biochemistry and Molecular Biology 2000; 74(5):357–364.[PubMed Abstract]
  31. van den Belt-Dusebout AW, Spaan M, Lambalk CB, et al. Ovarian stimulation for in vitro fertilization and long-term risk of breast cancer. JAMA 2016; 316(3):300-312.[PubMed Abstract]
  32. Gennari A, Costa M, Puntoni M, et al. Breast cancer incidence after hormonal treatments for infertility: systematic review and meta-analysis of population-based studies. Breast Cancer Research and Treatment 2015; 150(2):405-413.[PubMed Abstract]
  33. Brinton LA, Scoccia B, Moghissi KS, et al. Long-term relationship of ovulation-stimulating drugs to breast cancer risk. Cancer Epidemiology, Biomarkers & Prevention 2014; 23(4):584-593.[PubMed Abstract]
  34. Practice Committee of the American Society for Reproductive Medicine. Fertility drugs and cancer: a guideline. Fertility and Sterility 2016; First published online: August 26, 2016. doi: 10.1016/j.fertnstert.2016.08.035Exit Disclaimer.
  35. Rizzuto I, Behrens RF, Smith LA. Risk of ovarian cancer in women treated with ovarian stimulating drugs for infertility. Cochrane Database of Systematic Reviews 2013; (8):CD008215.[PubMed Abstract]
  36. Van Leeuwen FE, Klip H, Mooij TM, et al. Risk of borderline and invasive ovarian tumours after ovarian stimulation for in vitro fertilization in a large Dutch cohort. Human Reproduction 2011; 26(12):3456–3465.[PubMed Abstract]

Reviewed: November 9, 2016

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