According to a new study published in the journal PLoS One, 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.
For the study, researchers evaluated women's health histories, their babies birth weight, and their levels of three pregnancy hormones linked to breast cancer development: estrogen, anti-estrogen and insulinlike growth factors
They 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. These findings 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.
Study researcher Dr. Radek Bukowski, a professor of obstetrics and gynecology at the University of Texas Medical Branch in Galveston, said that the results demonstrate an association and not "a cause-and-effect link," meaning that women who give birth to fat firstborns shouldn't be too worried.
A woman's family history still remains the biggest indicator' when it comes to risk of developing breast cancer. Additionally, breastfeeding and having multiple children is known to decrease the risk of breast cancer.