Police in Masterton responding to an erratic driving complaint on Thursday found a woman who had crashed, was nearly four times over the drink-driving limit and had her young son in the car.

The 37-year-old mother of three crashed into a paddock before police were able to pull her over, Senior Sergeant Warwick Burr told The Dominion Post.

"Before a patrol could reach the area, she had crashed the car, ploughing through a farm fence and ending in a paddock. She blew 1594 micrograms of alcohol per litre of breath and was [going to be] charged with drunk driving," Mr Burr said.

The legal limit is 400mcg of alcohol per litre of breath.

Neither the woman nor her son were injured in the crash, which happened at night, apparently after she had been drinking with friends.

National road policing manager Superintendent Paula Rose said drink-drivers were frequently being caught with children in their cars and described the situation as a plague that was "incredibly disturbing".

Between 2007 and 2009, 12 children aged up to 14 died in cars driven by drunk people and 111 more were injured, the newspaper reported.