The woman's alleged assailant, Julianne Francis Williams, went on trial alongside co-accused Anthony Daniel McIver in the ACT Supreme Court on Tuesday.

Ms Williams, 38, has pleaded not guilty to charges of aggravated burglary and assault occasioning actual bodily harm.

Mr McIver, 32, denies being knowingly concerned in those crimes when they were allegedly committed in September last year.

In a police interview played to the court on Tuesday, the alleged victim said Ms Williams was the former girlfriend of the unborn baby's father.

She said she was "about to go on a picnic" when Ms Williams pulled up outside her Kambah home in a black Subaru with a man and Ms Williams' daughter, the latter of whom has not been charged.

The woman told police the trio got out and prevented her from being able to run as Ms Williams came up to the house and punched her "seven or eight" times.

She said she had ended up on the ground in the fetal position just inside her front door as she was attacked.

"I've just put my hands down to protect my stomach because that was her aim, to go for my stomach," she told police from a hospital bed not long after the alleged assault.

The woman claimed Ms Williams' daughter had told her to "just put your arms up and it'll all be over", but she refused as blows rained down on her.

"You could punch me 50 times in the head," she said.

"I'm not putting my arms up. You're not hurting my baby."

The woman also said Ms Williams had demanded before leaving the scene that "you better end it with him".

"Her intentions were to make me miscarriage [sic]," she said.

The court heard the expectant mother had been injured in the alleged attack, but her pregnancy had remained "intact".

Prosecutor Elizabeth Wren earlier told the court that in the lead-up to the incident, Ms Williams had warned the alleged victim that "she always comes out on top" and that "this will never end for you".

The prosecutor said police had arrived at the woman's home in the aftermath of the event to find her "crying and distressed and covered in blood".

Ms Wren also said the pregnant woman had been able to identify Ms Williams as her assailant because the pair had previously met.

She indicated she would allege the man present during the attack was Mr McIver, with forensics officers unable to rule out both he and Ms Williams as having contributed to DNA found on tracksuit pants that were stained with the victim's blood.

Ms Williams' barrister, Jack Tyler-Stott, said in brief opening remarks that there was "not a particularly strong basis" for the identification of his client as the attacker.

"The central issue [in the trial] will be one of identification," he told the court.

Mr McIver's lawyer, Jan de Bruin, declined to make an opening statement.

The judge-alone trial, before Justice Michael Elkaim, is expected to run for four days.

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