It is recognized that check details the microcirculation of the skin undergoes considerable modifications in the first few days or weeks of extrauterine life as the length and variability of the diameter of the capillaries increase [6] and BCD decreases progressively [39]. We have hypothesized that in singleton infants the abundant availability of nutrients after delivery presumably triggers a much more rapid and perhaps poorly controlled process of “capillary hyper-pruning,” culminating in these infants having capillary rarefaction by some

stage in later childhood [1, 14]. We speculate that this process of capillary hyperpruning may be less prominent or even absent in twin infants and this may explain the apparent lack of increased cardiovascular disease risk in these individuals in later life [20]. Another interesting observation in our study is the significantly lower family history of ischemic heart disease in the twin infants group. The significance of this finding is rather difficult to interpret but we cannot rule out a possible effect on the capillary density in these infants as we have previously reported that normotensive individuals with

RO4929097 nmr family history of essential hypertension have significant capillary rarefaction [4]. We acknowledge a major limitation in our study posed by the small numbers of twin infants but this emphasizes the difficulties in recruiting such infants. We also acknowledge the significant difference in the age of infants on the study day, as it was not always possible to perform capillaroscopy immediately after birth in the twin infants, who often had to be transferred to the neonatal unit. We feel it is essential to explain here how difficult it proved to study these new born infants who often wake up when they handled, and it then becomes difficult to proceed with the study as they become uncooperative and 3-mercaptopyruvate sulfurtransferase their mothers restless and anxious, and we often then had to abandon the study in as much as 25% of potential subjects. In conclusion, twin infants born with LBW or NBW to normotensive mothers have significantly higher functional and structural

skin capillary densities at birth compared to singleton infants. Further longitudinal studies of skin capillary density and of retinal vascular parameters commencing from birth to various stages in early childhood are essential to identify the dynamics and the exact timing, if any, of the remodeling of microcirculation in these individuals. LBW is a risk factor for adult hypertension and cardiovascular disease and is associated with functional and structural microvascular disease. Twin infants as a group tend to have LBW, but do not appear to have increased risk of cardiovascular disease in later life. When examined at birth, twin infants do not have a reduction in microvascular density but rather higher capillary count.