ExtractSkin reflectance in red, green, and blue light was measured at the sternum of 99 Caucasian infants ranging in gestational age from 26 to 44 weeks. Skin reflectance was consistently higher in female infants, but this difference was not statistically significant. Highly significant (P< 0.001) increases in reflectance at all wave lengths were found when sternal reflectance during the first 48 hr of life was related to gestational age. The dispersion of data points about the regression line does not permit this method to be relied upon as the sole means of determining gestational age of infants. Serial studies indicate that reflectance increases in premature infants not given phototherapy, whereas premature infants receiving photo-therapy show a fall in reflectance for the duration of therapy. This suggests that phototherapy may cause tanning of the skin.SpeculationReflectance spectrometry provides a safe, noninvasive method to assess human newborn skin maturation and may also be a means to determine effects of various therapeutic regimens on the skin.