When that mother and infant lock eyes, and the infant's old enough to have a social smile, what happens -- spontaneously -- is the eruption of joy on the part of the mother.
お母さんと赤ちゃんの目が合う時 赤ちゃんが人懐っこい微笑みを作れるようになると 自然にお母さんは喜びでいっぱいになります