Skin capillary density in infants born to normotensive mothers: a comparison between singleton and twin infants

Objective: Twin infants tend to have LBW and microvascular alterations but do not appear to have an increase in cardiovascular mortality later in life as singleton infants. We hypothesized that twin infants born to normotensive mothers would not have capillary rarefaction at birth.

Methods: We studied 26 dizygotic twin infants and compared them with 115 consecutive singleton infants to normotensive mothers. We used orthogonal polarized spectroscopy to measure basal (i.e., functional) and maximal (i.e., structural) skin capillary density according to a well-standardized protocol.

Results: Twin infants have significantly higher BCD (mean difference 4.3 capillaries/mm(2) , 95% CI: 0.4, 8.1, p = 0.03) and have marginally significantly higher MCD (mean difference 3.9 capillaries/mm(2) , 95% CI: -0.6, 8.3, p = 0.086) compared to singleton infants. Birth weight was significantly associated with BCD and MCD (p = 0.003 and 0.006).

Conclusions: Twin infants with low and NBWs tend to have higher functional and structural capillary densities 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.