Is There a Link Between Childbirth and Breast Cancer Risk?
Posted: Thursday, February 14, 2019
Women who have borne a child experience an increased risk for breast cancer for more than 20 years after the birth compared with nulliparous women, according to a pooled analysis of 15 prospective studies published in the Annals of Internal Medicine. In fact, for women who are older at first birth, multiparous, or have a family history of breast cancer, this risk may be enhanced.
“There are many ongoing studies that are trying to improve our ability to do breast cancer risk prediction on the individual level,” explained Hazel B. Nichols, PhD, of the University of North Carolina (UNC) Gillings School of Public Health, in a UNC press release. “This is one piece of evidence that can be considered for building new prediction models.”
This analysis aggregated data from 15 prospective studies from around the world, totaling 18,826 individual cases of breast cancer in women aged 55 years or younger. Compared with women who had never given birth, parous women had an increased risk for breast cancer that peaked 5 years after birth, at an 80% increased comparative risk. The increase in risk was particularly pronounced for childbearing women who had a family history of breast cancer. Risk was also greater for women who had given birth at an advanced age or who had borne multiple children.
The positive association between having a child and breast cancer risk did become a negative association around 24 years after having given birth. Breastfeeding did not appear to affect overall risk patterns, which seemed to be driven by estrogen receptor–positive breast cancer.
Disclosure: The study authors’ disclosure information may be found at annals.org.