The influence of the preterm gut microbiota in health and disease has been well established. However, relatively little is known about how the microbiome changes after discharge and its relationship with growth, health and disease outcomes in the preterm population. This study aims to follow a cohort of preterm infants and explore the relationship of the later microbiome ('after discharge') with later growth and health outcomes in infancy. The study will also explore the effect of timing of stopping routinely administered probiotics on the post-discharge microbiome, infant feeding and outcomes such as colic.