Police spokesman Paul J. Browne said Yoselyn Ortega, 50, was charged after investigators interviewed her at NewYork-Presbyterian/Weill Cornell Medical Center where she is recovering from self-inflicted cuts, The New York Times reported.
Ortega is accused in the Oct. 25 slayings of Lucia Krim, 6, and her brother, Leo, 2, at their Manhattan apartment. The attack occurred shortly before the children's mother, Marina Krim, returned from a swimming lesson with her other young daughter.
Ortega, a naturalized American citizen from the Dominican Republic, had worked for the Krim family for about two years. She had no previous criminal record and there had been no sign of trouble with the family, police said.
The Times said Ortega's relatives and friends have said she had been having mental issues recently.