One of Auckland's District Health Boards is investigating how unsanctioned and potentially dangerous advice was given to expectant mothers at an antenatal class.

Waitemata DHB is now tracking down parents who went to the publicly funded classes, at Waitakere Hospital.

A brochure was handed out with advice including to avoid medical intervention, and to try castor oil or acupuncture to bring on labour.

The DHB's Cath Cronin said the material was apparently generated by an individual staff member, and didn't go through the usual approval process.

She said it's extremely disappointing that some expectant mums and their partners have been given information which falls well short of the DHB’s standards and expectations.

Cath Cronin said the DHB is investigating how it happened as a matter of urgency, and staff have been instructed to find and take unsanctioned antenatal material out of circulation.