A baby’s size and shape at birth depends on how well they grow in the womb. Within the usual range, heavier (and longer) babies tend to become taller children and adults.
There is strong evidence that:
The evidence shows that, in general, the taller people are during adulthood and the more people weighed at birth, the higher their risk of some cancers.
Final adult height is linked to genetics, birthweight, rate of growth and age of puberty, as well as environmental factors that include nutrition. Periods of peak growth (such as in infancy and adolescence) are especially important in determining height, because growth is particularly sensitive to nutritional supply during these times. Growth is also especially dependent on the action of growth hormones and growth factors.
A baby’s birthweight and an adult’s height therefore both reflect a complex interplay of genetic, nutritional and other environmental factors that affect growth within the womb and during childhood and adolescence. Birthweight and height are markers of these factors. Neither birthweight nor height is likely to affect the risk of cancer directly.
Although adult attained height and birthweight are public health issues, as adults, people cannot modify these factors. It’s therefore inappropriate to make a global recommendation on height.
A baby’s size and shape at birth are an indication of the extent and quality of intra-uterine growth and development. Birthweight can be measured simply and reliably, whereas head circumference, which marks growth of the brain, and head-to-foot length, which marks linear growth, are more difficult to measure reliably. Within the usual range, heavier (and longer) babies tend to become taller children and adults.
Birthweight can predict the risk of death and of various diseases in infancy and later in life. Very low birthweight – less than 2.5 kilograms (5.5 lbs) for boys and 2.4 kilograms (5.3 lbs) for girls – increases the risk of perinatal death and disease, or death in infancy and young childhood, usually because of increased vulnerability to infection.
It’s well established, at least in high-income countries, that there is a graded relationship, throughout the normal range, between size at birth, and at one year of age, and risk of chronic disease such as cardiovascular disease and type 2 diabetes during adult life, such that lower weight predicts higher risk.
Very high birthweight may also be associated with increased risk of certain diseases – for instance, maternal diabetes or poor glucose homeostasis can cause higher birthweight as well as increased risk of diabetes in the infant. These findings have been shown to be independent of smoking tobacco or socioeconomic status, although they may be accentuated in the presence of these additional stress factors.
In 2018, we produced the Diet and Cancer Report, the third in our series of major reports looking at the many ways in which our diets, and how active we are, affect our cancer risk. You can find out much more about height and birthweight and the risk of cancer by downloading a pdf of the relevant chapter in the 2018 report. Please note, however, that this webpage may have been updated since the report was published.