Early nutritional origins of hypertension: a hypothesis still lacking support.

PURPOSE: It has been hypothesized that limitations in 'a baby's nourishment before birth', as reflected in reductions in birthweight and other newborn anthropometric measurements, are associated with subsequent elevations in blood pressure. We assess this hypothesis in light of four causal criteria commonly used by epidemiologists: specificity, consistency, strength and biological coherence. We also examine aspects of the methodology used in studies of this hypothesis. METHODOLOGIC PROBLEMS: Two major data sources for testing the hypothesis in Hertfordshire and Preston are flawed by very high attrition. The practice of testing this hypothesis by controlling for adult weight in the analysis overstates the benefit that might accrue from interventions to increase birthweight. CAUSAL CRITERIA: Studies used to support the hypothesis examine a wide variety of exposures and outcomes, without prespecification of which associations are expected. The inverse relationship of birthweight to blood pressure is found inconsistently and, when present, is not strong. Potential confounding variables, especially social class, have not generally been taken into account. Evidence from human nutrition studies, especially of famine exposure and pregnancy nutrition supplementation, are not supportive of the proposition that in industrialized countries variations in the birthweight of the population closely reflect pregnancy nutrition.
CONCLUSION: When examined critically, the evidence thus far provided does not support the hypothesis that prenatal nutrition is a major determinant of adult blood pressure.