Size at birth and blood pressure: cross sectional study in 8-11 year old children.

OBJECTIVE

To identify which patterns of fetal growth, represented by different measurements of size at birth, are associated with increased blood pressure in children aged 8-11 years.

DESIGN AND SETTING

School based, cross sectional survey conducted in 10 towns in England and Wales in 1994.

SUBJECTS

3010 singleton children (response rate 75%) with physical measurements and information on birth weight from parental questionnaires. Hospital birth records were examined for 1573.

MAIN OUTCOME MEASURES

Systolic and diastolic blood pressure at age 8-11 years.

RESULTS

In the whole group birth weight was inversely related to systolic pressure (regression coefficient -1.48 mm Hg/kg; 95% confidence interval -2.20 to -0.76) after adjustment for current body size. There was no significant association between birth weight and diastolic pressure. The association with systolic pressure was much stronger in girls (-2.54 mm Hg/kg; -3.60 to -1.48) than in boys (-0.64 mm Hg/kg; -1.58 to 0.30), with a significant difference between the sexes (P = 0.006). Among the other neonatal measures, head circumference and placental weight were inversely associated with subsequent blood pressure in girls, and placental ratio (placental weight:birth weight) was positively associated with blood pressure in boys. Neither ponderal index at birth nor length:head circumference ratio was related to blood pressure in either sex.

CONCLUSIONS

In these contemporary children the association between birth weight and blood pressure was apparent only in girls. There was no evidence that measures of size at birth, which may be related to nutrition at critical periods of pregnancy (thinness at birth or shortness in relation to head circumference), are related to blood pressure in the offspring.