Infants sleep in cribs rather than bassinets or toddler beds, and they can be bathed in bathtubs. They can also interact with Sims of all older life stages, as well as pets. Infants can be customized in Create a Sim and given unique traits.
It was announced at the Behind The Sims Summit teaser, with a clip of a crawling infant. It was added in patch 142, following the newborn stage and preceding the toddler stage. Infant is the second life stage in The Sims 4. An infant and her grandmother in The Sims 4: Growing Together.