BackgroundChildhood obesity is associated with elevated blood concentrations of inflammation markers. It is not known to what extent inflammation precedes the development of obesity.MethodsIn a cohort of 882 infants born before 28 weeks of gestation, we examined relationships between concentrations of 25 inflammation-related proteins in blood obtained during the first two postnatal weeks and body mass index at 2 years of age.ResultsAmong children delivered for spontaneous indications (n=734), obesity was associated with elevated concentrations of four proteins (IL-1β, IL-6, TNF-R1, and MCP-1) on the first postnatal day; one protein (IL-6) on postnatal day 7; and two proteins (ICAM-3 and VEGF-R1) on postnatal day 14. Among children delivered for maternal or fetal indications (n=148), obesity was associated with elevated concentrations of seven proteins on the 14th postnatal day. In multivariable models in the spontaneous indications subsample, elevated IL-6 on day 1 predicted obesity (odds ratio: 2.9; 95% confidence limits: 1.2, 6.8), whereas elevated VCAM-1 on day 14 predicted overweight at 2 years of age (odds ratio: 2.3; 95% confidence limits: 1.2, 4.3).ConclusionsIn this cohort, neonatal systemic inflammation preceded the onset of obesity, suggesting that inflammation might contribute to the development of obesity.