An infant trusts that its mother will raise it.

Literal

Infant [topic-は] mother [subject-が] raise-give-me [thing-こと] [object-を] believes.

育ててくれる ('raise [for one's benefit]') frames the mother's act as a favor done for the child. The nested clause 母親が育ててくれること functions as the object of 信じる. A philosophical sentence on trust and dependency.