Prosecutors say 27-year-old Yayun Weng was arrested after she brought her son, Ryan Gao, to a hospital on Thursday.
Authorities say doctors called police after observing bruises over the boy's entire body, multiple bite marks and swelling. The boy was listed in critical condition Saturday at Maimonides Medical Center.
The Daily News says Weng did not seek medical attention for her son until two days after the beating.
Weng, who speaks only Mandarin, pleaded not guilty at her arraignment Saturday on charges of assault, menacing, endangering the welfare of a child and harassment. She's being held on $50,000 bail and is next due in court on March 6.