The advent of universal newborn hearing screening coupled with new and improved hearing technologies have contributed to early identification of congenital hearing loss and early application of developmental intervention to improve outcomes of deaf and hard of hearing children. Evidence on the impact of significant (moderate to profound) bilateral hearing loss on children’s development and the effectiveness of treatment through amplification or cochlear implantation guide current best practice. However, the natural history and impacts of early detection and intervention (including early amplification) on outcomes in children with unilateral hearing loss or mild bilateral hearing loss are not well understood.