Systolic blood pressure in babies of less than 32 weeks gestation in the first year of life

Aim-To define the normal range of systolic blood pressure in a non-selectiv e population based sample of babies of low gestation throughout early infan cy. Methods-Daily measurements of systolic blood pressure were made in all the babies of less than 32 weeks gestation born in the North of England in 1990 and 1991 during the first 10 days of Life. Additional measurements were ob tained from 135 of these babies throughout the first year of life. Systolic pressure was measured by sensing arterial flow with a Doppler ultrasound p robe. It was assumed that blood pressure had never been pathologically abno rmal in the neonatal period if the child was alive and free from severe dis ability two years later. Data of adequate quality were available from 398 s uch children. Additional data were collected, for comparative purposes, fro m 123 babies of 32, 36, or 40 weeks of gestation. Results-Systolic pressure correlated with weight and gestation at birth, an d rose progressively during the first 10 days of Life. The coefficient of v ariation did not vary with gestational or postnatal age (mean value 17%), t he relation with gestation being closer than with birthweight. Systolic pre ssure rose 20% during the first 10 days from an initial mean of 42 mm Hg in babies of 24 weeks gestation, and by 42% from an initial mean of 48 mm Hg in babies of 31 weeks gestation. These findings were not altered by the exc lusion of data from 14 babies who had inotropic support during this time. S imultaneous measurements in three centres using an oscillometric technique revealed that this technique tended to overestimate systolic pressure when this was below average. Systolic pressure finally stabilised at a mean of 9 2 (95% CI 72-112) mm Hg at a postconceptional age of 44-48 weeks irrespecti ve of gestation at birth. Conclusion-Systolic blood pressure 4-24 hours after birth was less than ges tational age (in weeks) in only 3% of non-disabled long term survivors. Sys tolic pressure rose with increasing gestation and increasing postnatal age, but stabilised some six weeks after term, regardless of gestation at birth .