Objective. To examine the arterial blood pressure in the first week of life in a healthy premature population.

Design. Population-based cohort study.

Setting. Three intensive care nurseries in central New Jersey.

Patients. Premature infants with birth weights less than 2000 g.

Main Outcome Measures. We documented daily maximum and minimum systolic and maximum and minimum diastolic blood pressures during the first 7 days of life. To examine the effects on these ranges of blood pressure of specific risk factors likely to affect blood pressure, we identified four groups of infants: (1) healthy infants without any of the major risk factors (n = 193); (2) infants who were mechanically ventilated but free of any of the other conditions (n = 225); (3) infants with histories of maternal hypertension or preeclampsia (n = 38); and (4) infants with low Apgar scores (less than 3 at 1 minute and less than 6 at 5 minutes) regardless of the presence of other conditions (n = 86).

Results. Blood pressure increased steadily in the first week of life in all four groups. There was no relationship between any of the four blood pressure variables, or trends in blood pressure over time, with birth weight, gender, or race. Regression equations (based on all infants with available data) for blood pressure ranges by day of life revealed that the maximum systolic blood pressure increased by 2.6 mm Hg/d, the minimum systolic blood pressure increased by 1.8 mm Hg/d, the maximum diastolic blood pressure increased by 2.0 mm Hg/d, and the minimum diastolic blood pressure increased by 1.3 mm Hg/d.

Conclusions. Infants with birth asphyxia and ventilated infants had significantly lower systolic and diastolic blood pressures than healthy infants.

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