Effect of birth weight on life-course blood pressure levels among children born premature: The Cardiovascular Risk in Young Finns Study

Objectives: Both fetal growth restriction and prematurity have been associated with elevated blood pressure (BP). However, their combined effects on adult BP are unclear. Methods: Our analyses were based on 1756 participants in the population-based Cardiovascular Risk in Young Finns Study who had information on birth weight and gestational age, together with longitudinal data on cardiovascular risk markers from age 3-18 years in 1980 to age 34-49 years in 2011. Three groups were defined by birth data: those born at term (term); those born preterm (<37 weeks) with an appropriate birth weight (>-1 SD z score according to national sex and gestational week-stratified data) for gestational age (preterm appropriate birth weight for gestational age); and those born preterm with low birth weight (≤-1 SD z score) for gestational age [preterm small birth weight for gestational age (SGA)]. Results: There were no differences between the three groups in BP at baseline, but at the 31-year follow-up (mean age 41 years), mean SBP in the preterm SGA group was 7.2 mmHg (95% confidence interval=2.3-12.1 mmHg, P=0.004) higher than the preterm appropriate birth weight for gestational age group and 7.3 mmHg (95% confidence interval=5.2-9.4 mmHg, P<0.0001) higher than the term group, adjusted for age and sex. In addition, preterm SGA individuals had a higher prevalence of adult hypertension compared with those born at term (36.9 vs. 25.4%; age, sex, and risk factors adjusted P=0.006). Conclusion: These longitudinal data suggest that elevated BP levels associated with prematurity are more likely to be present in those with fetal growth restriction.