Did you know that your birth weight can predict whether you will develop heart disease, diabetes or certain other chronic diseases later in life? Wacky, but true.

Thanks to research into the Developmental Origins of Health & Disease (DOHaD) over the past 20 years, we know that babies born at the lower end of the normal birth weight range experience greater rates of chronic disease throughout life. Not only that, but babies born at five pounds have greater rates of adult heart disease and diabetes than babies born at six pounds, and those six pound babies have higher rates of disease than babies born at seven pounds. Babies born at nine pounds have the lowest rates of later chronic disease. The risk begins to climb again for babies born at the higher birth weights.

So how does this happen?

A baby’s birth weight is an indication of how she grew in the womb. The rate of a baby’s growth is set very early in development based on his environment, including his mother’s body size, amounts of fat and muscle, and the social stresses, like poverty and racism, she is exposed to. Birth weight is also affected by the size and shape of the placenta a woman develops. The placenta is the main transport system between the mother and her developing baby.

Babies in the womb are not completely reliant on the nutrition a woman receives during her pregnancy. From an evolutionary perspective, it would be too dangerous for a developing baby to be solely dependent on the food her mother ate on any given day. They draw on nutritional reserves the mother has built up within her body over her lifetime. So women who have not received nutritious foods have fewer reserves from which to draw.

Although a mother’s diet during her pregnancy is not closely linked with her baby’s birth weight, it does affect the baby’s vulnerabilities for later chronic disease. Humans are plastic, or malleable, during their development in the womb and adverse influences, such as poor nutrition or exposure to social stress, can permanently alter body structure and function. So babies that are exposed to these problems can be more likely to have chronic diseases later in life.

Resources in the womb are always limited to some degree. A developing baby prioritizes certain organs and systems over others. The brain is always the first priority, followed by the heart. Organs like the kidneys and the lungs, whose functions are provided by the mother until birth, are last on the list to receive resources. So a developing baby facing limited resources from the mothers nutrition will make trade-offs in development and protect the growth of the brain at the expense of these organs. Hence the association between low birth weight, certain lung problems, high blood pressure and diabetes.

Therefore, it is now clear that a host of chronic diseases, including heart disease, obesity and diabetes, lay their foundations before we are even born. These roots are formed in response to poor nutrition during growth in the womb. A baby that is malnourished in the womb is born vulnerable– with a propensity for disease that is very difficult to erase. The implications are clear: a good start is the foundation for a lifetime of health.

Chronic diseases are not an inevitable fact of aging. These diseases could be prevented if we as a society prioritized easy access to nutrition for all, with a focus on the health and nutrition of adolescent girls and young women. Not only would this reverse the disturbing trend of decreasing health in the U.S. and many other western nations, but it could prevent the rise of these chronic diseases in developing nations and lead to generations who will have better health and well-being throughout their lives.