Size at birth, infant growth, and blood pressure at three years of age.

OBJECTIVES: Our aim was to determine the extent to which infant growth-in weight-for-length-from birth to 6 months is associated with systolic blood pressure (SBP) at 3 years and to determine whether this association varies with birth size. STUDY DESIGN: In 530 children from the prospective cohort Project Viva, we measured birth length and 6-month weight and length with research standard instruments and SBP at age 3 years with a Dinamap automated recorder. We derived weight-for-length z-scores (WFL-z) and analyzed data with mixed effects regression models. RESULTS: The mean (SD) WFL-z was 0.47 (0.75) at birth and 0.70 (0.96) at 6 months. Mean (SD) SBP at 3 years was 91.7 (9.4) mm Hg. After adjusting for confounding variables and birth WFL-z, child SBP was 1.0 mm Hg (95% CI 0.2, 1.8) higher for each z-score increment in 6-month WFL-z. The SBP of children in the lowest birth WFL-z quartile and the highest 6-month WFL-z quartile was 5.5 mm Hg (95% CI 2.6, 8.4) higher than that of children in the highest birth and lowest 6-month WFL-z quartiles. CONCLUSIONS: More rapid increase in weight-for-length, a measure of adiposity, in the first 6 months of life is associated with higher early childhood SBP, particularly in children who are thin at birth.

Maternal age and other predictors of newborn blood pressure.

OBJECTIVE: To investigate perinatal predictors of newborn blood pressure. STUDY DESIGN: Among 1059 mothers and their newborn infants participating in Project Viva, a US cohort study of pregnant women and their offspring, we obtained five systolic blood pressure readings on a single occasion in the first few days of life. Using multivariate linear regression models, we examined the extent to which maternal age and other pre- and perinatal factors predicted newborn blood pressure level. RESULTS: Mean (SD) maternal age was 32.0 (5.2) years, and mean (SD) newborn systolic blood pressure was 72.6 (9.0) mm Hg. A multivariate model showed that for each 5-year increase in maternal age, newborn systolic blood pressure was 0.8 mm Hg higher (95% CI, 0.2, 1.4). In addition to maternal age, independent predictors of newborn blood pressure included maternal third trimester blood pressure (0.9 mm Hg [95% CI, 0.2, 1.6] for each increment in maternal blood pressure); infant age at which we measured blood pressure (2.4 mm Hg [95% CI 1.7, 3.0] for each additional day of life); and birth weight (2.9 mm Hg [95% CI, 1.6, 4.2] per kg). CONCLUSIONS: Higher maternal age, maternal blood pressure, and birth weight were associated with higher newborn systolic blood pressure. Whereas blood pressure later in childhood predicts adult hypertension and its consequences, newborn blood pressure may represent different phenomena, such as pre- and perinatal influences on cardiac structure and function.