Tony Ledbetter, 45, faces multiple counts of aggravated assault.
Police in South Dakota say they are shocked at the brutality the woman suffered.
Local news station Keloland reports the Sioux Falls woman”s ex-boyfriend is now behind bars accused of allegedly beating her and mutilating her with the steel tool.
The 39-year-old victim was taken to the hospital.
The woman, who is not being named because of the nature of the attack, was at her home when her ex-boyfriend came over to talk, which led to an argument.
“He ended up punching her in the face. Slamming her in the ground,” Sioux Falls Police Public Information Officer Sam Clemens told the television station.
As she pleaded with him, it is claimed he then he allegedly put his forearm against her neck and a blanket in her mouth.
Ledbetter appeared in court in Lincoln County facing several counts of aggravated assault and had his bail set at $250,000 (£205k) in cash.
A GoFundMe account has been set up for the victim where it was released his alleged victim is expecting his child.
The baby was not harmed but the victim will need extensive reconstructive surgery.