An ACT magistrate has "reluctantly" granted bail to a 24-year-old man accused of bashing his pregnant girlfriend to the point of hospitalising her with a potential brain injury.

During an argument last night, the man allegedly knocked the woman, who was 24 weeks pregnant, to the ground and then pushed her head into the floor again as he pinned her down, according to a statement of facts tendered to the court.

Court documents allege the man also picked his girlfriend up and swung her body from side to side, making "loud and unintelligible noises".

When the woman said she feared for her safety and the safety of the unborn child, the man allegedly began punching himself in the head, saying his girlfriend was "making him crazy".

The woman later contacted her brother, who took her to Calvary Hospital.

Police said when they visited the woman in hospital they saw that her face was bruised, there were marks and bruises on her neck and arms and she had grazes on her knees.

The man was charged with assault occasioning actual bodily harm, although the charges may be upgraded if medical examination reveals the woman or baby suffered brain injuries as a result.

The prosecution told the court it was an "incredibly serious assault" but did not argue for the man to remain in custody — something Magistrate Glenn Theakston noted when he granted bail.

"I do so with some reservation ... Certainly if it came before me I'd probably keep him in custody," he said.

Magistrate Theakston told the man: "I'm in two minds about granting you bail. I'm on a knife's edge."

He eventually did grant the man bail on the grounds that bail is generally favoured and because the man had no history of violent crime.

The man is expected to return to court later this month.