Proposed Link Between Female Birth Weight and Likelihood of Breast Cancer

I was watching the BBC News this morning, when I heard about a recent piece of research which claims to provide the strongest link yet between the birth weight and length of a female child and her likelihood of developing breast cancer later in life. It is estimated that 5% of all breast cancers could be explained by birth weight. Just a 0.5 kg (or 1 lb) increase in birth weight was deemed to correspond to a 7% increase in the risk of cancer.

The weird thing about this estimated increase in the risk is that it is of a similar magnitude to the estimate for other more well-known risk factors, such as alcohol consumption.

We can all do a lot while pregnant to give our child the best possible start in life (ie limited alcohol consumption, good diet, no smoking etc), but the dimensions of our child are possibly a little outside the realm of our control. Then combine this with the general upward trend in birth weights and sizes in the first world. Where are we going?