A Sydney gamer has pleaded guilty to assaulting his pregnant partner after their argument was inadvertently live-streamed as he played Fortnite.

Luke James Munday pleaded guilty to common assault on Monday before magistrate Ian Cheetham in Picton Local Court.

The Telstra network engineer and his partner Grace Campbell argued over his online gaming activity on Sunday, December 10, last year, according to the agreed statement of facts.

Ms Campbell asked him to stop and eat dinner, and when he refused, she went into the office area of their home and told him she wanted him to eat with the family.

She asked him several times and each time he said he would be out soon.