Tradesmen found the infant inside a drain on La Salle Road in Alexander Heights about 1pm (3pm AEDT) on Monday.
Homicide squad detectives today charged a 31-year-old woman with one count of concealing the birth of a deceased baby.
It comes days after police made a public appeal for the mother of the baby to come forward.
She is expected to appear before Perth Magistrates Court on September 12.