Blood pressure and heart rate during stress in children born small for gestational age

Increased sympathetic nervous system activity has been proposed as a potential mechanism for the blood pressure (BP) elevation seen in individuals born small for gestational age (SGA). This study was carried out to detect the changes in BP and heart rate (HR) in children born SGA during exposure to stress and to assess for changes in urinary catecholamine excretion. Nineteen children aged 6-14 years born SGA and 17 age- and gender-matched healthy controls were included in the study. The stress test included a mathematical test and venipuncture. BP and HR were monitored during the test. Spot urine samples were collected at baseline and after the stress test to determine dopamine, epinephrine and norepinephrine levels. At baseline, there was no difference in BP and HR between the SGA and control groups, but mean urinary norepinephrine levels were slightly higher in the SGA group (55.7 +/- 16.1 vs. 43.4 +/- 3.8 mcg/gCr; P = 0.10). Compared to the control group, mean maximal HR increase was higher in the SGA group (31.3 +/- 3.1 vs. 19.2 +/- 3.8%; P = 0.008), and mean duration of maximal HR to baseline HR was longer (186 +/- 23 vs. 97 +/- 13 s, respectively; P = 0.003). There was a significant negative correlation between birth weight and maximal HR increase (r = -0.497, P = 0.003). Children born SGA showed significantly greater increases in HR and significantly longer periods of tachycardia during exposure to stress than did healthy controls. The rise in HR was inversely correlated with birth weight. These findings suggest that children born SGA have a greater increase in sympathetic response when exposed to stress than do healthy individuals.