Size at birth and blood pressure in early adolescence: a prospective birth cohort study.

Previous studies have suggested that birth size may influence blood pressure in later life. Most of these reported inverse associations only became evident after weight or body mass index at some later age was included in the regression model. In a prospective birth cohort study in Brazil, the effect of birth size on blood pressure at age 11 years was explored. Of the 5,249 cohort members, 4,452 were interviewed. Mean systolic and diastolic blood pressures were 101.9 mmHg (standard deviation, 12.3) and 63.4 mmHg (standard deviation, 9.9), respectively. Birth weight was positively associated with blood pressure in the crude analysis, but this effect was no longer significant after adjustment for confounders. When current body mass index-a possible mediating variable-was added to the model, the association between birth weight and blood pressure tended to become negative, though not quite significant. Birth length showed a positive effect on later blood pressure regardless of the adjustments made. Head circumference, gestational age, and ponderal index were not associated with blood pressure. Children born small for gestational age had lower blood pressure values. The postulated inverse association between birth weight and later blood pressure was not confirmed in this cohort. Instead, a positive effect of birth length was detected.