Childbirth and breast cancer risk – time to think again?

While we’re aware that there are many factors that come into play when it comes to the development – or non-development – of breast cancer, we’ve been led to believe that childbirth can give women a long-term boost towards the prevention of breast cancer. However, new research from America suggests that this benefit isn’t an instant development.

The study has been conducted by the American College of Physicians, a national organisation of internists based in Philadelphia which is the largest of its kind in the USA, which examined data from 15 studies worldwide from over 800,000 women. And the results suggested that breast cancer risk actually elevates for a time in women who had given birth and were aged 55 or younger.

A long wait for added protection

According to the study, this risk hit its peak about five years after women had given birth, with mothers in this age range having an 80% higher chance of developing breast cancer compared with those women who had not gone through childbirth. And the authors were keen to point out that this risk appeared to be more prominent for women who fit into one of three categories: those who had a family history of breast cancer, people who were older at the time of their first birth, or those who had had more children overall. Breastfeeding appeared to have no impact.

The key finding from the study was that this elevated breast cancer risk disappeared on an average of 23 years after childbirth – and after more than two decades, women began to experience a form of protection from the disease. This is a significant rewriting of one of the tenets of breast cancer prevention and could have major repercussions in future understandings of breast cancer.

“What most people know is that women who have children tend to have lower breast cancer risk than women who have not had children, but that really comes from what breast cancer looks like for women in their 60s and beyond,” claimed Hazel B. Nichols, PhD, one of the study authors. “We found that it can take more than twenty years for childbirth to become protective for breast cancer, and that before that, breast cancer risk was higher in women who had recently had a child.”

Age counts too

Another key finding was that the age of a woman’s pregnancy had a bearing on the elevated risk of breast cancer, and it appears that younger first-time mothers – those under 25 – saw no increased risk in cancer development, while women who had their first child after the age of 35 experienced a higher risk.  However, the research team were extremely keen to stress that the overall chance of getting breast cancer was still relatively low for any woman who had given birth.

So, what can be learned from this study? Well, the research team hope that the findings will be taken on board by the medical community to develop a more useful model for breast cancer risk – which, in turn, could lead to more effective screening and prevention methods. But they’re aware that the results concluded that pregnancy is only long-term protection against oestrogen receptor-positive breast cancer – and there are more types of breast cancers around which childbirth has no bearing upon.