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In Reply.— We would like to thank JM Perlman and JJ Volpe for their comments on our recent article.1 They were surprised that we did not observe the "excessive" levels of blood pressure fluctuation (coefficient of variation up to 30% or more) which they obtained for cerebral blood flow velocity in infants at greatest risk of developing IVH (Perlman et al2,3). We were surprised by this too; and, as we commented in the discussion, this disparity is difficult to explain.

A total of 22 infants of less than 31 weeks' gestation who were mechanically ventilated for a minimum of 12 hours for respiratory distress syndrome were studied. The coefficient of variation of direct systolic pressure was measured each minute from six to 36 hours of age and averaged per hour after birth with a microcomputer-based system of data collection. At the start of recording, the ultrasound scan appeared normal in each infant, but intraventricular hemorrhage developed in ten infants less than 36 hours of age. Twelve infants remained free of intraventricular hemorrhages. BP fluctuation was greater for a longer proportion of measured time in infants in whom intraventricular hemorrhage did not develop compared with those in whom it did develop P < .05). These findings do not support a causal relationship between BP fluctuation and intraventricular hemorrhage within the range of coefficient of variation studied.