Women whose firstborn children weighed more than 8.25 pounds at birth have more than double the risk of getting breast cancer, compared to women who have smaller babies according to a new study. The findings, published in the journal PLoS One, suggest that giving birth to a big baby creates a hormonal environment in the mother that's conducive to the development of breast cancer in women later in their lives.

Researchers evaluated women's health histories, their babies birth weight, and their levels of three pregnancy hormones: estrogen, anti-estrogen and insulinlike growth factors. (These hormones are linked to breast cancer development.) The found that women whose firstborn babies had a high birthweight had higher levels of estrogen and insulinlike growth factors during pregnancy, as well as lower anti-estrogen levels.

However, these results demonstrate an association, not "a cause-and-effect link," said the study researcher Dr. Radek Bukowski, a professor of obstetrics and gynecology at the University of Texas Medical Branch in Galveston, meaning that women who have fat firstborns needn't be alarmed.

Additionally, breastfeeding and having multiple children is known to decrease the risk of breast cancer. However, fat babies, breast feeding, and a litter of kids can only go so far in determining a woman's likelihood of breast cancer, as her family history remains the biggest indicator.

Image via Shutterstock/Boris Ryaposov

Women with big firstborn babies may have higher breast cancer risk [MSNBC]