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13 SEX DIFFERENCE IN CEREBRAL BLOOD FLOW (CBF) OF PREMATURE INFANTS

Sex differences in CBF-values have been demonstrated in adults. The purpose of our study was to evaluate the effect of sex on the resting cerebral blood flow in premature neonates.Methods: Sixty-eight premature babies with a gestational age of less than 34 weeks and a birth weight of less than 1500g were studied. No difference in regard of blood pressure, arterial CO2- and O2-partial pressures, and hematocrit between the sexes were observed. CBF was measured with the non-ivasive intravenous 133Xenon method three times under resting conditions. Depending on the time of the CBF-study we classified our measurements into three groups: Group 1; Measurement 2-36 hours after birth (N=46). Group 2; 36-108 hours (N=39). Group 3; 108-240 hours (N=41).Results: Average CBF in group 1 (12.5 ± 3.5 ml/100g/min) was significantly lower (p<0.05) then in group 2 (14.6 ± 3.8 ml/lOOg/min) and in group 1 (14.2 ± 3.3 ml/100g/ min). No significant difference between groups 2 and 3 was found. CBF values, grouped by sex, are shown in the table.Discussion: Girls had significantly lower cerebral blood flows than boys in all three age groups. From adult studies we know that under resting conditions men have a lower blood flow than women. It is not surprising that differences seen in adults can also be demonstrated in newborns. However the reasons for the reversed laterality effects are unclear since the neurophysiologica! mechanisms involved are not known. We conclude that in preterm neonates the cerebral blood flow is substantially influenced by sex.