This project involves assessing the genetic contribution to the determination of body composition at birth. Fetal and early postnatal life has been well demonstrated as a period of metabolic "programming" with the potential to influence a wide of adult diseases. Clearly there is contribution from, and interaction between, various genetic and environmental influences to determine and individual's outcome in the face of the early life environment.

Early work in this field first identified birth weight as an indicator of growth during pregnancy, but subsequent work has shown that birth weight is a somewhat crude measure, and more information can be gained by using more refined assessments of early life growth. Ponderal index is a measure of body composition that has been well validated at birth. It is analogous to the adult body mass index (with body length cubed, rather than squared as in BMI) compensating for body mass compared to length (height), and is well correlated to other measures of adiposity. Compared with birth weight, ponderal index is better at identifying "asymmetrically" growth restricted neonates in whom we suspect metabolic stressors to be greater than constitutionally small babies.

This project is a collaborative approach among members of the Early Growth Genetics Consortium. Cohorts with appropriate genetic data will use a genome-wide approach to identify genetic loci associated with changes in ponderal index. Each cohort will run individual analyses according to a uniform multivariate model, and then meta-analysis will look at all of the cohorts in combination. Attempts at replication of significant findings will be made in other birth cohorts without complete GWAS data. With an anticipated total number exceeding 10,000 individuals, this study will be well powered to show the relatively small changes associated with single genetic variants. This will be the first GWAS of ponderal index to be performed.