Cardiovascular risk factors at age 30 following pre-term birth

Recent epidemiological evidence has shown increased rates of cardiovascular mortality and associated risk factors in those born small. However, scarce information exists concerning cardiovascular risk factors in adulthood following pre-term birth, or distinguishing the relative contributions of length of gestation and fetal growth to small size at birth.

Prospective follow-up of 458 30-year-olds whose mothers took part in a randomized controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome (147 born at term, 311 born pre-term). Follow-up assessments included anthropometry, blood pressure, blood lipids, early morning cortisol levels and 75 g oral glucose tolerance test.

Gestational age at birth, pre-term birth, and birth weight z-score were not associated with serum cholesterol, triglyceride or cortisol at age 30 (P > 0.1 for all). However, pre-term birth was associated with increased systolic blood pressure (3.5 mmHg, 95% CI 0.9-6.1 mmHg, P = 0.009) and insulin resistance at age 30 [Log (Insulin area under the curve) = 0.17, 95% CI 0.05-0.28, P = 0.006]. Low gestational age at birth was also associated with these outcomes, whereas birth weight, adjusted for gestational age, was not.

Adults who were born moderately pre-term have increased blood pressure and insulin resistance at 30 years of age. Pre-term birth rather than poor fetal growth is the major determinant of this association. As both the incidence of pre-term birth and survival amongst those born pre-term are increasing, this group may contribute an increasing proportion to overall cardiovascular disease burden.