Birth weight and blood pressure: cross sectional and longitudinal relations in childhood.

Introduction

Barker and colleagues argued that early life factors, acting particularly in utero, may have a strong influence on subsequent cardiovascular risk.[1] An inverse relation between birth weight and subsequent blood pressure (lower birth weight being associated with higher subsequent mean blood pressure) has been reported in adults[2-4] and children,[2 5-8] though not consistently in adolescents.[9-11] Earlier reports also suggested that a large placenta, particularly in the presence of low birth weight, was related to subsequent high blood pressure and the risk of hypertension.[3] Recent reports have suggested that the birth weight and blood pressure relation becomes stronger with age ("amplification")[12] and that this may be an example of "programming"[13] However, the evidence for amplification is based almost entirely on comparison of cross sectional studies with subjects of different ages and times of birth rather than on longitudinal measurements.[14]

We studied the relation between birth weight and blood pressure in children. In cross sectional analyses at 9-11 years of age we examined the relations between birth weight and blood pressure and the influence of placental weight. In longitudinal analyses based on children measured at both 5-7 and 9-11 years of age we examined the development of the birth weight and blood pressure relation with age.

Subjects and methods

We present data based on two surveys four years apart (1987 and 1991) in Guildford and Carlisle. The sampling and methods used have been detailed elsewhere.[6 15 16] Both surveys were carried out in the same sample of 10 primary schools in each town. The second survey included all children from the earlier survey still attending the schools together with similar numbers of children in the same classes. In both surveys measurements were made by a team of trained nurse observers, who visited schools in the two areas in sequence.

Blood pressure was measured after five minutes, rest with the child seated and the arm supported at chest level. Three blood pressure measurements were made one minute apart on the right arm with the Dinamap 1846SX oscillometric blood pressure recorder (Critikon Inc, United States).[17] All analyses were based on the means of the three readings. At 9-11 years all measurements were made with the adult size cuff (cuff bladder 22 cmx 12 cm); at 5-7 years all measurements were standardised to the child size cuff (cuff bladder 15 cmx9 cm), as described.[18] These cuff sizes ensured that the minimum cuff bladder width to arm circumference ratio of 40% recommended by the American Heart Association[19] was met for 98% of the study population at age 9-11 years and for 99% of the population at age 5-7 years Ethnic …