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A new study finds that women who gain a large amount of weight during pregnancy face a
higher risk of developing breast cancer after they reach menopause.
The researchers attribute the increased breast cancer risk to a higher amount of estrogen
that is produced in fat cells, which may be especially harmful as the breast undergoes
rapid changes during pregnancy. Still, the researchers acknowledge that the risk of breast
cancer appears to be relatively small for women who gain a significant amount of weight
during pregnancy. Furthermore, women who retain the extra weight after pregnancy tend to
be at higher risk of post-menopausal breast cancer than those who lose the excess pounds
after childbirth.
Researcher Leena Hilakivi-Clarke, PhD presented the study findings at the annual
meeting of the American Association for Cancer Research (AACR), held in April 2002.
To conduct the study, Dr. Hilakivi-Clarke and her team analyzed medical records from over
27,000 Finnish women. The first analysis consisted of 17,360 women, including 98 women who
developed pre-menopausal breast cancer at an average age of 47. The second analysis was
made up of 3,209 women, 185 of whom developed post-menopausal breast cancer at an average
age of 58.
Based on their analyses, the researchers concluded that women who gained more than 38
pounds during pregnancy faced a 40% greater risk of developing post-menopausal breast
cancer, compared with women who gained less weight. Weight gain during pregnancy was not
associated with an increased risk of breast cancer before menopause.
"We also found that women who retain the added pounds after pregnancy are at the
greatest risk. These additional pounds may induce changes in breast tissue that increase
susceptibility to breast cancer in later life," said Dr. Hilakivi-Clarke, as quoted
in an AACR news release. "Overall, the increased risk due to pregnancy weight gain is
modest – equivalent to the increased risk from obesity after menopause."
According to Dr. Hilakivi-Clarke, previous data have found that women who gain a large
amount of weight during pregnancy have higher estrogen levels than women who gain less
weight. The study suggests that the higher a woman's estrogen levels, the higher her risk
of developing post-menopausal breast cancer.
Though the study found that more than 38 pounds gained during pregnancy increased
breast cancer risk, Dr. Hilakivi-Clarke said that obstetricians recommend gaining 25 to 35
pounds during pregnancy and that this amount of weight gain was not associated with a
higher risk of breast cancer, before or after menopause.
Despite this latest study, the link between weight and breast cancer risk remains
controversial. Several small studies suggest that overweight (obese) women who gained
their excess weight as adults are at an increased risk of developing breast cancer, but
women who have been overweight since childhood are not at any significantly higher risk.
Also, overweight women who take hormone replacement therapy may
be at greater risk of developing breast cancer. In an interview with the Associated
Press, Dr. Eugenia Calle, Director of Analytic Epidemiology at the American Cancer
Society, said that significant weight gain during pregnancy may not be any more harmful
than weight gain in general.
Additional Resources and References
- The study, "Pregnancy Weight Gain and Mother’s Breast Cancer Risk," was
presented at the annual meeting of the American Association for Cancer Research
(AACR) from April 6-10, 2002, http://www.aacr.org/
- This article references the April 9, 2002 Associated Press report, "Weight
Gain, Cancer Risk Linked: Too Much Weight Gain During Pregnancy May Increase Breast Cancer
Risk."
- To learn more about breast cancer risk factors, please visit http://www.imaginis.com/breasthealth/bc_risks.asp
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