The man, who cannot be named in order to protect the identity of both his daughter and his then 17-year-old girlfriend, pleaded guilty to 18 domestic violence charges in Wollongong Local Court relating to the abuse of the young woman over a four-day period last September.

The assaults occurred in the days after Family and Community Services removed the couple's 10-week-old daughter from their care in late August after caseworkers noticed bruising on the child's face.

A subsequent medical examination of the child found she had seven fractures to her ribs, all of which were at different stages of healing, indicating multiple assaults. She also had a fractured right wrist.

Police planted a covert listening bug inside the couple's home, which recorded the father admitting he'd "karate-chopped" the girl and squeezed her ribs.

The listening device also detected the man carrying out multiple assaults on his girlfriend, who was pregnant with their second child.

In one instance, while the pair were arguing over the man's penchant for spending their limited funds on pet fish, he called her a "f--king dog c--t", while later that same day he threatened to break her jaw, then hit her.

Meanwhile, the man also tried to choke the teen and told her "my pregnant f--kin girlfriend's not leaving this f--king house tonight in one f--king piece".

He was also overheard telling the girl later that same day "I hope you know I'm kicking that f--king kid out of your gut before you leave my house".

The man was arrested on October 1 and charged with recklessly causing grievous bodily harm over his assault on his child. Judge Chris O'Brien sentenced him to 4 years and 6 months' jail in Wollongong District Court earlier this month, with a non-parole period of 2 years and 10 months.

He found the man had "limited, if any, insight into his offending".

"He told [the psychologist] that he believed he was performing the functions of parenthood adequately," Judge O'Brien said.

"He could not have been more mistaken."

Meanwhile, Magistrate Claire Girotto dealt with the offences against the man's partner in Wollongong Local Court on Friday, labelling him a "repeat domestic violence offender".

"You have an inability to manage your anger and frustration when things don't go your way and this leads to violence," she said.

"You also lack insight into what triggers your offending."

She sentenced him to 14 months' jail, with a 7-month non-parole period, which partially overlaps with his current sentence.

He had been due to be released from prison in September next year but will now be released to parole in February 2022.