Formal or literary term for a very young baby; in everyday speech 赤ちゃん is more common.
That hospital puts effort into the health management of infants.
She picked up the infant and gently soothed it.
infanticide
Sino-Japanese compound of 嬰 (ei, 'newborn') and 児 (ji, 'child'). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning 'infant'.