The comments of Shohat and colleagues are well taken. The change in peripheral venous hematocrit with postnatal age observed by them is a well known phenomenon that has been reported previously.1 The changes in viscosity should be expected in the newborn as the blood viscosity determination parallels the hematocrit. The assumption that the umbilical venous hematocrit level would parallel these changes is not entirely correct.

In a preliminary investigation involving 32 infants we determined the correlation between mixed cord blood hematocrit, peripheral venous (PVHct), and umbilical venous hematocrit (UVHct).

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