The characteristic ruddy hue of a newborn's skin is primarily due to what?

The characteristic ruddy hue observed in a newborn's skin is primarily due to increased red blood cell concentration. After birth, infants often experience a high level of hemoglobin and red blood cells, which can give their skin a pink or reddish appearance. This is especially noticeable in newborns, who may have a higher erythrocyte count as a response to the transition from the intrauterine environment to breathing air. Increased blood flow and the presence of oxygenated hemoglobin in the capillaries also contribute to this color, making it a normal physiological characteristic of healthy newborns.

In contrast, genetic variation influences many aspects of skin color across different populations but does not specifically account for the ruddy hue in newborns. The lack of melanin typically leads to lighter skin tones rather than a ruddy hue. Dehydration can lead to a different skin appearance, often resulting in pallor or a dry look rather than the healthy, rosy complexion typically seen in well-hydrated, healthy newborns. Thus, the increased concentration of red blood cells is the primary factor for the ruddy hue in newborns.