Shaun Leitch, 33, also hit the woman on the head with an ashtray and punched her to the ribs during repeated attacks at their home in Ballymena, Co Antrim.
Sending him to prison, the judge stressed: “This is a bad episode.”
Leitch, of Ballyclug Mews in the town, pleaded guilty to three counts of common assault and threats to kill his partner.
Antrim Magistrates’ Court, sitting in Belfast, heard violence flared after she arrived home on the morning of April 5.
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Accusing the woman of having been with someone else, he cornered her in the kitchen, grabbed her by the ponytail and threw her against kitchen cupboards.
While she was on the floor he kicked her on the thigh.
Police went to the address, but the woman claimed they had just been arguing and didn’t want to get Leitch in trouble.
Later the same day, however, he asked her to get drugs and threw crockery at her when she was unable to do so.
“He hit her on the back of the head with an ashtray,” a Crown lawyer said.
“During this incident he picked up a kitchen knife and said ‘Do you want me to cut the wain out of you?’”
Leitch then grabbed her by the throat and pushed her against a door when she tried to leave.
“He punched her to the ribs and banged her head on the wall repeatedly,” the prosecutor said.
At one point the woman tried to defend herself, but while she was on top of him he threatened: “Once I get up I’m going to kill you.”
She then fled to a neighbour’s apartment for protection.
Leitch initially claimed the woman had smashed his TV and head-butted him.
He also accused her of being a prostitute and a drug addict.
During subsequent interviews he accepted that he might have slapped and kicked her if she struck him.
Defence solicitor Stewart Ballentine told the court Leitch now realised his “toxic” relationship with the woman was over.
“At the time both of them were in a bad place, and with lockdown this was exacerbated,” the lawyer said.
Mr Ballentine disclosed that the woman has just given birth, and emphasised his client’s desire to play a parental role.
“Like any father he would be anxious to have a first glimpse of his child as soon as possible,” he added.
But imposing seven months custody, District Judge Fiona Bagnall said: “One of the strong aggravating factors is this lady must have been seven months pregnant when these offences occurred.”