The birth size – breast cancer link

Do you know that your size at birth may actually tell you whether you are susceptible to breast cancer later in life? Yes, new findings showed that birth size, particularly birth length, may be related to risk of breast cancer in adulthood and this information can be used as an indicator for susceptibility to this type of cancer for women.

This is based on the association study led by Isabel dos Santos, a professor of Epidemiology at the London School of Hygiene and Tropical Medicine. In this study, the researchers reviewed 32 published and unpublished studies, comprising of 22,058 cases of breast cancer among 600,000 women from developed countries. They re-analysed the data to determine the relationship between birth size and risk of breast cancer in adult women. The information on birth size was based on birth records of all participants. The three birth size measures that were examined were birth weight, birth length and head circumference.

The researchers found that women with higher birth weight tended to have higher risk for breast cancer. The analysed data showed that 0.5 kg increase in birth weight may increase the risk of breast cancer by 7%. Birth length and head circumference are also found to be indicators of breast cancer risk. Birth length was especially found to be the strongest predictor for breast cancer.

According to dos Santos Silva,

‘Our study indicates that birth size is a marker of susceptibility to breast cancer in adulthood, at least in developed countries. The birth size – breast cancer association appeared to be largely independent of known risk factors. Little is known on how the pre-natal environment may affect breast cancer risk later in life. Further research is needed to unravel the biological mechanisms underlying the birth size – breast cancer association’.

Specifically, the women who were found to be at higher risk were:

• those with birth length of 51 cm or more.
• those whose head circumference was 35 cm or more.
• those who weighed more than 4 kg at birth.

The results are especially relevant considering the trend of many babies being overweight at birth due to maternal health factors.

According to experts at the Harvard University School of Public Health who were not part of the research, the new study provides “the strongest evidence yet that birth size is a critical determinant of breast cancer risk in adult life.”

Unfortunately, the study cannot explain the reason behind this birth size – breast cancer association. Let us hope that future research will bring some clarifications.

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