A woman’s breast cancer risk more than doubles as a result of delivering a high-birth-weight infant, according to research published recently in PLoS ONE. Researchers from the University of Texas Medical Branch at Galveston suggest that a large infant is linked to a hormonal environment during pregnancy that promotes future breast cancer development and progression in the mother.
The research builds on accumulating evidence that a woman’s own birth weight and that of her children are linked to breast cancer. Marking the first time that high birth weight is shown to be an independent risk factor, the study findings may assist with prediction and prevention of breast cancer decades before its onset.
Lead author Dr Radek Bukowski, professor of obstetrics and gynecology in the Division of Maternal-Fetal Medicine, and his team examined 2 groups of women from The Framingham Offspring Birth History Study and The First and Second Trimester Evaluation of Risk for Aneuploidy (FASTER).
Bukowski’s team studied 410 women from the Framingham study. To determine breast cancer risk, these patients’ maternal birth weight, infant birth weight, and results of later examinations (eg, breast cancer diagnosis) were observed between 1991 and 2008. The researchers also looked at data from the study on known breast cancer risk factors, such as age, race/ethnicity, body mass index, diabetes, use of hormone replacement therapy, and maternal history of the disease, among others.
Between 1999 and 2003, the FASTER trial examined pregnancy hormones in nearly 24,000 women at 15 US clinical centers. The study included assessments of estriol (E3), anti-estrogen alpha-fetoprotein (AFP), and pregnancy-associated plasma protein-A (PAPP-A), the hormones that affect infant birth weight and breast cancer risk.
Approximately 7.6% of the Framingham patients in this study were later diagnosed with breast cancer. Additionally, the risk of breast cancer was 2.5 times higher in women whose infant’s birth weight was in the top quintile compared with women whose infant weighed in the lower quintiles. Researchers note that the risk was shown to be independent of the birth weight of the mother and traditional breast cancer risk factors.
Within the FASTER trial, a strong positive correlation was detected between infant birth weight and E3, AFP and PAPP-A concentrations. For women whose infant’s birth weight was in the highest quintile, there was a 25% increased risk of having a high E3/AFP ratio and PAPP-A concentration.
“We also found that women delivering large babies – those in the top quintile of this study, which included babies whose weight was 8.25 or more pounds – have increased levels of hormones that create a ‘pro-carcinogenic environment.’ This means that they have high levels of estrogen, low levels of anti-estrogen and the presence of free insulin-like growth factors associated with breast cancer development and progression,” said Bukowski. “Women can’t alter their pregnancy hormones, but can take steps to increase their general protection against breast cancer.”
Breast-feeding, having more than 1 child, following a healthy diet, and exercising have been shown to reduce breast cancer risk, notes Bukowski.