The generic word used to indicate any woman, other than the mother, who takes care of a child is tata (feminine, plural: tate) in Italian. Some possible translations in English include babysitting, nanny and childminder.

Usually, tata denotes a woman whose full-time profession is childminding, rather than a teenager or young woman who occasionally babysits. (The latter is usually referred to with the English word babysitter pronounced with an Italian accent!)
Ho fatto la tata a tempo pieno presso una famiglia benestante di Torino.
I worked as a full-time nanny for a wealthy family from Turin.

Tata is onomatopoeic in that it mimics baby talk, much like the words nanna (nap / sleep) and pappa (baby food / mush).
Some possible synonyms for tata include:
- balia = a woman who a) sells her milk to another mother, or b) takes care of a baby in the place of the mother
- bambinaia = a salaried woman who is responsible for the care and custody of young children in a family
- governante = a salaried woman who takes care of the house and gives the children an education (governess)