Professor C Mary Schooling co-authors “Birth weight and risk of ischemic heart disease: A Mendelian randomization study.”
The World Health Organization has classified low birth weight as a risk factor for cardiovascular disease. However, this advice is based on observational studies which might indicate that lower birth weight causes cardiovascular disease or might indicate that people who have heavier babies are healthier for other reasons, such as higher socio-economic position. In the absence of randomized controlled trials showing the effect of birth weight on major diseases, Professor Schooling and colleagues compared the risk of ischemic heart disease and type 2 diabetes by genetically predicted birth weight. People with genetically lower birth weight did not clearly have a higher risk of ischemic heart disease, although they did have a higher risk of type 2 diabetes. This study casts doubt on birth weight contributing to ischemic heart disease consistent with observations in monozygote twins, where any difference in birth weight is unrelated to cardiovascular disease.
In summary, Professor Schooling says, “Lower birth weight may increase the risk of type 2 diabetes, but is unlikely to make a substantial contribution to cardiovascular disease. Interventions to prevent cardiovascular disease should be sought elsewhere and recommendations based on high quality evidence.”