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As researchers continue to search for risk factors that may increase the chances of
breast cancer, a new study shows that birth weight may play a role. In the study,
scientists found that heavier babies were more likely than lighter babies to develop pre-menopausal breast cancer. The researchers
attribute the increased breast cancer risk to hormonal factors exerted on babies in the
womb. Further research on the pre-natal environment may provide more answers about future
cancer risk.
To investigate whether the size of a baby at birth and the rate of growth influence
breast cancer risk later in life, Valerie McCormack, a research fellow at the London
School of Hygiene and Tropical Medicine, and colleagues studied 5,358 Swedish females born
between 1915 and 1929. They found that 359 of the women developed breast cancer.
McCormack and her team found that the women who weighed 8 pounds, 13 ounces (4,000
grams) or more at birth were 3.5 times more likely to develop pre-menopausal breast cancer
compared to the women who weighed 6 pounds, 10 ounces (3,000 grams) or less at birth.
However, birth weight only affected the risk of developing breast cancer before menopause;
weight did not play a factor in post-menopausal breast cancer risk (post-menopausal breast
cancer is significantly more common than pre-menopausal breast cancer).
In fact, the researchers say that the breast cancer risk they found in their study was
less associated with actual birth weight. Rather, it was linked to a baby’s length
and head size. Women who were longer babies and those born with bigger heads were more
likely to develop pre-menopausal breast cancer.
McCormack and her colleagues say that hormonal influences in the womb are a likely
explanation for the association between birth characteristics and the risk of
pre-menopausal breast cancer. Those further research is needed to investigate this link,
the researchers suggest that larger babies may be exposed to different levels of growth
hormones in the womb that increase the chances for pre-menopausal breast cancer. Factors
that can influence hormones in the womb include a mother’s nutritional habits,
variations in natural hormones, and whether or not a mother smokes during pregnancy.
This study highlights ongoing research on causes of breast cancer. While several
factors have already been identified as contributing to breast cancer risk (including
advanced age, early onset of menstruation, late menopause, not having children, long-term
use of hormone replacement therapy, etc.), approximately 80% of
women who develop breast cancer have no known risk factors. Research is also focused on
genes and gene-environment interactions that may increase breast cancer risk.
Additional Resources and References
- The report, "Fetal Growth and Subsequent Risk of Breast Cancer: Results from Long
Term Follow Up o Swedish Cohort," is published in the February 1, 2003 issue of the British
Medical Journal, http://bmj.com/
- The January 31, 2003 Reuters Health report, "Larger Babies, Higher Future
Risk of Breast Cancer," by Alison McCook is available to paid subscribers at www.reutershealth.com
- To learn more about risk factors for breast cancer, please visit http://www.imaginis.com/breasthealth/bc_risks.asp
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