A pregnant woman, and a mother driving two young children, have been nabbed in a drink-diving blitz.

The mother, a 35-year-old from the Hibiscus Coast, north of Auckland, was stopped by police in the afternoon, and caught at double the legal limit - blowing 835 micrograms of alcohol per litre of breath. The legal limit is 400 micrograms.

Her children were aged two and six months, and police have referred the case to CYF.

Another woman caught was six months pregnant. The 23-year-old had a breath alcohol reading of 540 micrograms.

A third woman, aged 49, had the highest reading - 979 micrograms - and the trio have been charged with driving with excess breath alcohol.

The Hibiscus Coast blitz earlier this month was to reinforce the results of Easter's zero road toll, and police say 25 people were caught.

''Fortunately she [the mother] was caught during this operation,'' Rodney police Sergeant John Roberts said.

"Individuals who are planning to drink and socialise should consider engaging a sober driver or make alternative arrangements whereby they can effectively plan a safe arrival home after an enjoyable night out.

''The simple facts are evident. If you drink and drive, you most certainly will be caught.''