A Rotorua schoolteacher has admitted beating his pregnant wife after she told him their child was a girl, not the boy he wanted.

Shiu Nadan, 52, pleaded guilty in Rotorua District Court to one count of possession of a weapon, one of male assaults female, one of common assault and three of threatening to do grievous bodily harm to his wife and stepdaughters.

Nadan, a former chemistry teacher at Rotorua Boys' High School and former Western Heights High relief teacher, was heavily intoxicated at the time of the February 8 incident, the Rotorua Daily Post reported.

According to the police summary of facts for the case, the argument erupted when Nadan's wife told him she was pregnant with a girl.

Nadan first threatened to hit the woman with a beer bottle, then to induce labour by kicking her in the stomach.

He then threatened to chop up his two stepdaughters - unimpressed they had enrolled at school under their own surname and not his - and hang their bodies up in the house.

He then took off his leather belt, told them he was going to "smash you guys so hard" and swung it towards them.

Nadan then kicked his wife and one of the girls in the legs. After facing several more threats of being cut into pieces, the mother and daughters escaped to a friend's house and called police.

The former teacher also pleaded not guilty to a charge of driving while disqualified. He would return to court on March 23 to defend the driving charge and May 6 to be sentenced on the domestic violence charges.