Breastfeeding protects the mother? While we generally
focus on the positive benefits of breastfeeding for the infants, there are additional
benefits for the mother as well. Breastfeeding has been found to provide a measure
of protection against uterine, cervical and ovarian cancers as well as breast cancer.
A study by Yale University researchers showed that women who
breastfed for two years or longer reduced their risk of breast
cancer by 50 percent. The researchers studied the medical history
of 808 Chinese women in the rural Shandong province from 1997 to
1999. The women were aged 30 to 80 and half had breast cancer and
half did not. The study was published in the American
Journal of Epidemiology. Although the study did not explore the reasons why
breastfeeding appears to lower the risk of breast cancer, some
researchers say it could be because breastfeeding reduces exposure
to estrogen, and yet another theory is that fat-soluble pollutants
and carcinogens are not stored as much in lactating breasts than
in non-lactation breasts.
One theory of how breastfeeding may help protect women from
ovarian cancer is that breastfeeding reduces the total number of
ovulations. The full mechanism by which breastfeeding provides protection is not fully
understood, but we can measure the results. In the following you will find studies
on breastfeeding's protective effects on mothers. These studies were originally
published in such journals as the 'New England Journal of Medicine', 'American Journal of
Epidemiology' and 'Journal of Clinical Epidemiology'.
References:
Breast Cancer
In 1999, a group of researchers at the Fred Hutchinson Cancer
Research Center in Seattle published the findings of their study
of postmenopausal breast cancer risk according to breastfeeding
characteristics.
For the study, the researchers contacted 3,633 breast cancer
patients aged 50 to 79 from Massachusetts, New Hampshire and
Wisconsin. More than 3,700 women of similar age were randomly
selected to serve as the control group. The researchers obtained
the women's lactation histories and breast cancer risk factors
though telephone interviews.
After adjusting the statistics for age, parity, age at first birth
and other breast cancer risk factors, the researchers found that
breastfeeding for at least two weeks was associated with a
slightly reduced risk of breast cancer compared to women who have
never lactated. Their findings also modestly suggested that women
who breastfed longer had a greater reduced risk of breast cancer
than those who breastfed for shorter periods of time.
The researchers found no evidence that suggested age at first
lactation was associated with breast cancer risk. Also, the use of
hormones to suppress lactation was not associated with
postmenopausal breast cancer, nor was the inability to breastfed
related to risk.
The researchers did conclude, however, that lactation may have a
slight and perhaps long-lasting protective effect on
postmenopausal breast cancer risk.
Other research
Among both premenopausal and postmenopausal women, risk of breast cancer decrease with
increasing duration of lifetime lactation experience although the effect was consistently
stronger for premenopausal women.
Source: McTieman, A., "Evidence of Protective Effect of
Lactation on Risk of Breast Cancer in Young Women." American Journal of Epidemiology,
1986
After controlling for age at first full term pregnancy and other potentially
compounding factors, parity and duration of breast feeding also had a strong influence on
the risk of breast cancer. Compared with parous women who never breast fed, women who had
breast fed for 25 months or more had a lower relative risk.
Source: Layde, P.M., "The
Independent Associations of Parity Age at First full Term Pregnancy, and Duration of
Breast Feeding with the Risk of Breast Cancer." Journal of Clinical Epidemiol, 1989.
If women who do not breastfeed or who breastfed for less than 3 months were to do so
for 4 to 12 months, breast cancer among parous premenopausal women could be reduce by 11%;
if all women with children lactated for 24 months or longer, the incidence might be
reduced by nearly 25%.
Source: Newcomb,P. etal. "Lactation and reduced risk of premenopausal
breast cancer." N Engl J Med 1994; 330(2):81-87.
Women who were breastfed as infants, even if only for a short time, showed an
approximate 25% lower risk of developing premenopausal or postmenopausal breast cancer,
compared to women who were bottle-fed as an infant.
Source: Freudenheim, J. "Exposure to
breast milk in infancy and the risk of breast cancer." Epidemiology 1994 5:324-331
An increasing duration of
lactation was associated with a statistically significant trend toward a reduced risk of
breast cancer.
Sources: Newcomb, P.A. et al. 1994 Lactation and a reduced risk of premenopausal breast cancer. The New England Journal of Medicine 330(2):81-87. (P Byers T, et al. Lactation and breast cancer: evidence for a negative
association in premenopausal women. American Journal of Epidemiology Vol 121, pp664-74,
1985)
Siskind V, et al. Breast cancer and breastfeeding: results from and Australian
case-control study. American Journal of Epidemiology, Vol 130, pp229-36, 1989
Uterine Cancer
A protective effect against uterine cancer was found for women who breastfeed.
Source: Brock,
K.E., "Sexual, Reproductive, and Contraceptive Risk Factors for Carcinoma-in-Situ of
the Uterine Cervix in Sidney. " Medical Journal of Australia, 1989.
Ovarian Cancer
Breastfeeding should be added to the list of factors that decrease
ovulatory age and
thereby decrease the risk of ovarian cancer.
Source: Schneider, A.P. "Risk Factor for Ovarian
Cancer. "New England Journal of Medicine, 1987
Endometrial Cancer
Lactation provides a hypoestrogenic effect with less stimulation of the endometrial
lining. This event may offer a protective effect from endometrial cancer.
Source: Petterson B, et
al. "Menstruation span- a time limited risk factor for endometrial carcinoma". Acta Obstet Gyneocol Scand 1986;65:247-55
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