The victim struggled to breathe and later went to hospital to be assessed.
The following month the couple clashed again, this time while lying in bed.
Middlemiss accused the victim of messaging other men and when she attempted to hug him, he threw her arm away.
They stood up and he punched her in the face.
By April 4, Middlemiss was on bail on the condition that he not contact the woman, who was 11 weeks' pregnant.
The victim woke to find the defendant in bed with her.
She asked Middlemiss to leave the address and, sensing his temper erupting, pleaded with him not to hit her.
"I don't care - it's not my f***ing baby," he said.
Without warning, he then punched the victim in the right side of her stomach.
Along with the violence, Middlemiss was yesterday sentenced on two counts of driving while suspended and three breaches of intensive supervision.
Defence counsel Brian Kilkelly said his client was truly remorseful for his actions.
"He regrets he won't be there for birth of their first child," he said.
Mr Kilkelly told the court Middlemiss' errant behaviour was the result of a raging drug addiction which had him taking opioids four times a week and cannabis daily.
The defendant was motivated to address that and had already enrolled in the drug treatment unit in prison, he said.
Despite the repeated episodes the victim, who was in court yesterday, opposed a protection order being made in her favour.
Middlemiss was banned from driving for eight months and nearly $7000 of fines he had racked up were remitted by Judge Kevin Phillips.
In September, RNZ reported nearly 1300 strangulation charges had been laid, resulting in 47 convictions.
