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Delivering a large infant more than doubles breast cancer risk

Robin Wulffson MD's picture
breast cancer, large infant, hormone levels, risk, health lifestyle

According to a new study, delivering an infant with a high birth weight more than doubles the risk of breast cancer. Researchers from the University Texas Medical Branch at Galveston published their findings on July 17 in the journal PLoS One.

The researchers noted that previous studies have reported that a woman’s risk of breast cancer in later life is associated with her infant’s birth weights. In view of this, the researchers set out to determine whether this association is independent of breast cancer risk factors and the mother’s own birth weight. In addition, they evaluated the association between the infant’s birth weight and hormonal environment during pregnancy. They noted that an independent association would have implications for not only understanding the mechanism of breast cancer development but also for the prediction and prevention of breast cancer.

The study group was comprised of 410 women enrolled in the Framingham study. The researchers assessed the risk of breast cancer in relation to a first infant’s birth weight, mother’s own birth weight, and breast cancer risk factors, Serum concentrations of estriol (E3), anti-estrogen alpha-fetoprotein (AFP), and pregnancy-associated plasma protein-A (PAPP-A) were measured in 23,824 pregnant women from a separate prospective study: the FASTER trial. During an average follow-up of 14 years), 31 women (7.6 %) were diagnosed with breast cancer. Women with large birth weight infants (in the top 20%) had a 2.5 fold higher breast cancer risk compared to other women. The finding was not affected by adjustment for birth weight of the mother and traditional breast cancer risk factors. An infant’s birth weight had a strong positive relationship with the mother’s serum E3/AFP ratio and PAPP-A concentration during pregnancy. Adjustment for breast cancer risk factors did not have a material effect on these relationships. The researchers noted that larger infants appear to promote certain levels of hormones during pregnancy that increase a woman’s risk of cancer. Specifically, this ‘pro-carcinogenic environment’ includes high levels of estrogen, low levels of anti-estrogen, and the presence of free insulin-like growth factors, which are associated with the progression of breast cancer.

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The authors concluded that giving birth to an infant with high birth weight was associated with increased breast cancer risk in later life, independently of mother’s own birth weight and breast cancer risk factors. Furthermore, it was associated with a hormonal environment during pregnancy favoring future breast cancer development and progression. They note that further studies must be conducted before clinical recommendations based on their results can be made.

Take home message:
Factors associated with delivering a large infant include excessive weight gain and gestational diabetes. Factors that reduce the risk of breast cancer include: maintaining a healthy weight, engaging in physical exercise, and eating a healthy diet. In addition, breastfeeding has been reported to reduce the risk of brast cancer.

Reference: PLoS One

See also:
Reduce your breast cancer risk with exercise
FDA accelerates drug approval for patients with aggressive breast cancers