Hundreds of midwives are going on strike today, promising "maximum disruption" for District Health Boards while not putting women and babies at risk.
Union members on duty will stop work for two hours at 11am and then again at 9pm.
Midwives Union spokesperson Jill Ovens said the industrial action would continue twice a day for two weeks across various shifts.
"The idea of strike action is to cause disruption, but we don't want to cause disruption to women and their babies. That's why we're doing just two-hour strikes."
Workers would remain at the hospital but would not perform all their usual tasks during each two-hour period, Ms Ovens said.
"They won't be answering call bells unless people have an emergency," she said.
"Sometimes people push their call bell because they want their jug of water filled. They most certainly won't be doing that sort of thing."
The midwives would step in if there were "life-preserving situations", such as a woman giving birth, she said.
"Somebody who is in labour will be looked after for two hours after the birth."
The action would be enormously disruptive for DHBs, she said.
"Almost all the employed midwives in DHBs around the country belong to the Midwives Union ... it's been a huge logistical nightmare for the DHBs' management and that's the idea."
Ms Ovens said midwives wanted to negotiate their own pay and conditions rather than being expected to accept the same agreement as the Nurses' Organisation.
"They are different professions. We're not saying there's anything wrong with the nursing profession. It's an honourable profession in its own right, but they're not the same," she said.
"No one would question it if you said, 'oh well, physiotherapists or occupational therapists or doctors should have the own pay scales that reflect the qualifications and skills'.
"And yet why are we questioning why midwives can't have that as well?"
Ms Ovens said the union is asking DHBs to pay newly graduated midwives a minimum of $56,000 a year.
However she told Morning Report that DHBs have been unwilling to negotiate even when the two parties held urgent mediation talks last week.
"We think that they (DHBs) have had this pattern of bargaining where one group is just meant to roll over and accept the settlement that another group has made without considering the merits of different cases that are being put forward by the different unions," she said.
DHBs' spokesperson Jim Green said the priority was the safety of women and children, and DHBs had contingency plans to ensure they had access to the services they need.
Mr Green said the offer to MERAS midwives, including a 9 percent pay rise over the next 18 months, two pay step increases and a lump sum payment, and would deliver a significant pay increase.
It was the same pay deal offered to those covered by the NZ Nurses' Organisation, he said.
"DHBs are keen to keep talking to the union and we will continue trying to settle these negotiations," Mr Green said in a statement.
"Work is underway at a sector level looking at wider workforce planning matters and midwives also have a pay equity claim that is being considered. These are the appropriate forums for these wider workforce issues."