Fetal growth and subsequent risk of breast cancer: results from long term follow up of Swedish cohort BMJ Volume 326, pp 248-51
A study in the BMJ this week finds an association between size at birth and risk of pre-menopausal breast cancer.
Over 5,000 women born in Sweden during 1915-29 were included in the study, of which 63 had breast cancer before the age of 50. There were strong positive associations between measures of birth size and rates of breast cancer at pre-menopausal ages, even when other adult risk factors were taken into account. Birth length and head circumference had stronger associations with pre-menopausal breast cancer than birth weight.
In addition, a shorter period of pregnancy was independently associated with an increased risk of breast cancer before the age of 50, indicating that "the rate of fetal growth may underlie the association between birth size and risk of early breast cancer" suggest the authors.
There was no evidence of an association between birth size and breast cancer in post-menopausal women, of which 296 had breast cancer.
However, the authors explain that in public health terms, if the findings were real, large birth size would be responsible for only a small proportion of the total number of cases of breast cancer in any population, as the incidence at premenopausal ages is low. Moreover, this association should be considered in light of its opposite association with heart disease, a much more common condition, they conclude.