Delayed early-childhood social milestone development 2013-11-23T08:40:29Z HP:0012434 This term may be applied to describe a child whose social development is delayed compared to age-related norms. For instance, at the age of three months, a child smiles in response to social interaction;. aAt the age of seven months, a child responds to the facial expressions of others;. aAnd at the age of 12 months, a child is shy around strangers. UMLS:C4022906 Delayed social development Delayed milestone development A failure to meet one or more age-related milestones of social behavior. Neurodevelopmental delay Abnormal social development