Yet when the birth records of these subjects were traced, birth weight correlated very closely with both measures of vascular physiology, and the relationships were strongly dependent on the intermediate phenotype of a high waist-to-hip ratio, in other words central obesity. These observations might suggest that capillary rarefaction, consequent upon intrauterine growth retardation, may have a part to play in linking insulin resistance and hypertension. It might be interesting to speculate that parallel renal vascular abnormalities could underlie a non modulating phenotype. The role of central obesity as a mediator of the effect of low birth weight is also worth exploring.