On Wednesday police charged a 24-year-old woman over a critically injured child in North Rocks. The two-year-old boy has been hospitalised for one week in a critical condition.
Police had already charged a 39-year-old man with inflicting grievous bodily harm over the same case on Friday.
The child was taken to Westmead Hospital with serious head and body injuries on Wednesday, July 30.
On Friday, police arrested the man and the woman, but released her without charge pending further inquiries.
The man has already appeared in court.
On Wednesday, police arrested the woman again and later charged her with inflicting grievous bodily harm (principal in the second degree), hindering a police investigation and failing to provide for a child, causing danger of death.
She was refused bail and appeared in Parramatta Local Court the same day.
The child remains in a critical but stable condition.