Stockholm, Sweden - Medical and technological advances have made it possible for more preterm babies to survive into adulthood, making a new population of adults with unknown health risks. However, a recent study by Stefan Johansson, MD et al. from the Karolinska Institute in Stockholm, Sweden published in the November 29, 2005 issue of Circulation showed that young men who were born preterm have a higher risk of high systolic blood pressure than men born at or beyond full term. They also showed that the risk for high systolic blood pressure increases as gestational age decreases.

Individuals born with a gestational age of 29 to 32 weeks are thought to have structural changes in their vascular tree and higher systolic blood pressures than those born at term. Johansson et al. designed a cohort study to evaluate the relationships between gestational age, birth weight for gestational age, and body mass index with regard to the risk of high blood pressure in adulthood. The study participants were selected from 4 population-based Swedish registers and included 404,306 men, of which 82% had available information on systolic and diastolic blood pressure from the conscription registry for military service which is mandatory for all ambulatory Swedish men.

The risk of high systolic blood pressure in men born extremely preterm (24 to 28 weeks) was twice that of men born at term (37 to 41 weeks; adjusted odds ratio (OR) 1.81, 95% confidence interval (CI), 1.30-2.52). This risk consistently decreased as gestational age increased, so that men born postterm (42 to 43 weeks) had an adjusted OR of 0.91 (95% CI, 0.89-.94). Compared to men born at an appropriate birth weight for gestational age, men born with a small birth weight for gestational age were 10% more likely to have high systolic blood pressure (adjusted OR 1.09, 95% CI, 1.04-1.14). Only men born moderately preterm (33 to 36 weeks) had a significantly increased risk of high diastolic blood pressure (adjusted OR 1.25, 95% CI, 1.02-1.53). In regard to high systolic blood pressure (> 140 mmHg), small birth weight for gestational age was not a risk factor among men born at 24 to 32 weeks. However, the risk of high systolic blood pressure increased among men with longer gestational age (33 to 36 weeks, 37 to 41 weeks, and 42 to 43 weeks) and small birth weight for gestational age (adjusted OR 1.33, 95% CI, 1.12-1.57, P = 0.03; adjusted OR 1.09, 95% CI, 1.03-1.15, P = 0.03; adjusted OR 1.21, 95% CI, 1.09-1.34, P = 0.03, respectively).

The major finding of this study is the increasing systolic blood pressure with decreasing gestational age. Thus, this study suggests that measurement of blood pressure is indicated any time a preterm-born child presents for health care. In addition, routine blood pressure follow-up and active interventions in childhood may be warranted in preterm-born individuals.

Co-authors: Anastasia Iliadou, MSc, PhD; Niklas Bergvall, MSc; Torsten Tuvemo, MD, PhD; Mikael Norman, MD, PhD; Sven Cnattingius, MD, PhD.