Journal of Paediatric Medicine & Surgery
Open Access

Lower birth weight and preterm birth have been linked to increased blood pressure in later life in two meta-analyses and systematic reviews. A meta-analysis of 27 research looking into the relationship between birth weight and blood pressure discovered that subjects with birth weights less 2.5 kg had 2.28 mm Hg higher systolic blood pressures than those with birth weights over 2.5 kg. Many studies fail to distinguish between low birth weights caused by growth restriction (an intrauterine stress signal) at any gestational age or preterm birth with an adequate (low) weight for gestational age.

As a result, determining the relative influence of growth restriction and preterm birth on subsequent blood pressures might be difficult. A study of 50-year-old adults born at term but with or without growth restriction found that those who had experienced growth restriction had an odds ratio (OR) of 1.9 for hypertension when compared to those who had normal birth weights. As a result, growth limitation prior to birth is linked to increased blood pressure later on.

Preterm subjects, with a mean gestational age of 30.2 weeks and a mean birth weight of 1280 g, had 2.5 mm Hg higher (95 percent CI: 1.7 to 3.3 mm Hg) systolic blood pressures in later life than those born at term, according to a systematic review of 10 studies comparing preterm or very low-birth-weight subjects versus those born at term. As a result, preterm delivery is linked to elevated blood pressure, which in some studies fits the criterion of hypertension by the age of 1-2 years.

However, it is unclear if preterm participants who were born small for gestational age (growth restricted) have a higher risk of high blood pressure than those who were born at the normal gestational age. Some studies imply an additional effect of growth restriction, while others do not. Finally, the importance of distinguishing between the risks of low birth weight "versus" preterm birth may lie in the future potential for prevention, but, given that effect estimates for the risk of higher blood pressures were similar in the meta-analyses and systematic reviews cited earlier, both events must be regarded as important risk factors for subsequent high blood pressure at this time.

Importantly, blood pressures in low-birth-weight and normal-birthweight persons may be within the normal range in childhood, but differences get exacerbated with age, such that adults who were born underweight frequently have overt hypertension that worsens with age. Although the majority of studies have been conducted in Caucasian groups, data from other populations is becoming more consistent.

Some studies have found a link between higher blood pressure and lower birth weight in African-American children, but not all, suggesting that other factors may play a role in the severity of blood pressure among African-Americans. Current body mass index, which may overcome an effect of birth weight, especially in children at various stages of growth, is a key effect modifier of the link between low birth weight or preterm delivery and blood pressure, which has been observed in several populations. Furthermore, blood pressure is highest in individuals born preterm or with a low birth weight who "catch up" the fastest in postnatal weight (i.e., rapid upward crossing of weight centiles) in most populations, underscoring the relevance of early postnatal nutrition in developmental programming.