Aims: A critical period for important processes involved in brain development, such as synapse and dendrite formation, neural pruning, and myelination, begins in utero and continues through the first few years of life. Infection in infancy may compete with bodily resources that are otherwise necessary to promote normal growth and development during this critical period. We aim to evaluate whether a mother's report of her baby's infection during the first 6 months of life is associated with birth weight and early childhood growth patterns, whether infection is associated with cognitive measures in childhood, and whether the association of infection with cognitive measures can be explained in part by slower growth patterns.

Hypotheses:1. Increased infection in infancy will associate with lower birth weight and slower childhood growth trajectories. 2. Increased infection in infancy will associate with poorer performance on cognitive tests. 3. The association of increased report of infection with lowered cognitive test performance will attenuate after control for growth measures.

Exposures: Maternal report of baby's infection during the first 6 months. We wish to use latent classes of infection as defined by Hepworth et al. 2010 EJE. Outcomes: Clinic and parental report of height and weight measures from birth to 10 years; WPPSI at 4 years and WISC-III at 8 years of age; Strength and Difficulties Questionnaire; other tests of memory, attention and developments (see data required above) ; we will consider educational outcomes as they become available.