BIRTH-WEIGHT AND BLOOD-PRESSURE - CROSS-SECTIONAL AND LONGITUDINAL RELATIONS IN CHILDHOOD

Objective-To examine cross sectional and longitudinal relations betwee n birth weight and blood pressure in childhood. Design-Cross sectional study of primary school children aged 9-11 years, with analysis in re lation to previous measurements at 5-7 years in a subgroup. Setting-20 primary schools in Guildford and Carlisle. Subjects-1511 children mea sured at 9-11 years (response rate 79%), including 549 who had been me asured at 5-7 years. Main outcome measures-Blood pressure at 9-11 year s, change in blood pressure between 5-7 and 9-11 years, birth weight ( based on maternal recall), and placental weight (based on birth record s). Results-At 9-11 years birth weight was inversely related both to s ystolic blood pressure (regression coefficient -2.80 mm Hg/kg; 95% con fidence interval -3.84 to -1.76) and to diastolic blood pressure (regr ession coefficient -1.42 mm Hg/kg; -2.14 to -0.70) once current height and body mass index were taken into account. Placental weight was inv ersely related to blood pressure after adjustment for current height a nd body mass index but placental ratio (placental weight to birth weig ht) was unrelated to blood pressure. Between 5-7 and 9-11 years systol ic blood pressure rose more rapidly in children of lower birth weight (regression coefficient -1.71 mm Hg/kg; -3.35 to -0.07). This effect s eemed to be stronger in girls. Conclusions-Birth weight rather than pl acental ratio is the early Life factor most importantly related to blo od pressure in childhood. The results support the possibility of ''amp lification'' of the relation between birth weight and blood pressure, particularly in girls.