Systematic review and meta-analysis of preterm birth and later systolic blood pressure

Abstract

Lower birth weight because of fetal growth restriction is associated with higher blood pressure later in life, but the extent to which preterm birth (<37 completed weeks' gestation) or very low birth weight (<1500 g) predicts higher blood pressure is less clear. We performed a systematic review of 27 observational studies that compared the resting or ambulatory systolic blood pressure or diagnosis of hypertension among children, adolescents, and adults born preterm or very low birth weight with those born at term. We performed a meta-analysis with the subset of 10 studies that reported the resting systolic blood pressure difference in millimeters of mercury with 95% CIs or SEs. We assessed methodologic quality with a modified Newcastle-Ottawa Scale. The 10 studies were composed of 1342 preterm or very low birth weight and 1738 term participants from 8 countries. The mean gestational age at birth of the preterm participants was 30.2 weeks (range: 28.8-34.1 weeks), birth weight was 1280 g (range: 1098-1958 g), and age at systolic blood pressure measurement was 17.8 years (range: 6.3-22.4 years). Former preterm or very low birth weight infants had higher systolic blood pressure than term infants (pooled estimate: 2.5 mm Hg [95% CI: 1.7-3.3 mm Hg]). For the 5 highest quality studies, the systolic blood pressure difference was slightly greater, at 3.8 mm Hg (95% CI: 2.6-5.0 mm Hg). We conclude that infants who are born preterm or very low birth weight have modestly higher systolic blood pressure later in life and may be at increased risk for developing hypertension and its sequelae.

Figure 1

Screening and selection of studies included in the systematic review and meta-analysis

Figure 2

Assessment of methodologic quality for observational studies, adapted from the Newcastle-Ottawa Scale. Stars were awarded if the study met the listed criteria. The maximum possible score was 7. VLBW is very low birth weight (<1500g) and NICU is neonatal intensive care unit.

Figure 3

Meta-analysis of the difference in SBP between participants born preterm or VLBW vs. full term. Small solid circles represent the estimated BP difference from each study, shaded squares represent the sample size, and solid horizontal lines represent the 95% confidence intervals. The open diamond and dashed vertical line represent the pooled SBP difference, and the solid vertical line represents the null hypothesis, no SBP difference. Weights are from the random effects analysis. Panel (A) includes 10 observational studies. Panel (B) includes the 3 studies that adjusted for a measure of socioeconomic status. Panel (C) includes the 8 studies that adjusted for a measure of attained size (height, weight, or BMI). Panel (D) includes only very preterm (≤32 weeks) or very low birth weight (<1500 grams) participants. Panel (E) includes the 5 higher quality studies.

Figure 4

Funnel plots with (A) 10 observational studies of preterm or VLBW birth and SBP and (B) 5 higher quality studies. Circles represent studies. Small study effects are visually apparent in (A) for 2 studies^, with larger effect sizes and greater variability (larger standard errors), P=0.04 and in (B) for 1 study, P=0.29.