London School of Hygiene & Tropical Medicine

Women who had a greater birth size have a significantly higher risk than others of developing pre-menopausal breast cancer, according to a study carried out by the London School of Hygiene & Tropical Medicine.

The study, reported in the British Medical Journal today, looked at 5,000 women born in Sweden during 1915-29, of which 63 had developed breast cancer before the age of 50 and 296 at or over age 50 years. Larger birth size was found to be associated with increased rates of breast cancer at pre-menopausal ages, even when other adult risk factors were taken into account. Birth length and head circumference were found to have stronger associations than birth weight. Shorter pregnancies were also found to carry an increased risk at pre-menopausal ages, independent of birth size.

Birth size was not found to be associated with breast cancer risk at post-menopausal ages.

The authors conclude that the findings suggest that the rate of fetal growth may underlie the association between birth size and the risk of early breast cancer. However, it is important to keep the findings in perspective as the incidence of premenopausal breast cancer is very low and birth size has an opposite association with heart disease, a more common condition.

You can contact Valerie McCormack on 020 7927 2301 or at valerie.mccormack@lshtm.ac.uk

End