Ardern, 37, said she will continue working as close as possible to her due date of June 17 and then hand over power to her deputy Winston Peters.
New Zealand's pregnant Prime Minister, Jacinda Ardern, on Monday revealed her government's plans for running the country after she gives birth and takes six weeks maternity leave.
Mr Peters and Ms Ardern were quick to defend the letter when asked whether it was a "behave-yourself contract".
"Can I just say the Prime Minister and I crafted this letter...any anyone that says otherwise, to use Geoffrey Palmer's favoured phrase, is spreading rumour with malice". "In many ways, it will be as per usual but simply our roles will reverse for a time". It reflected what was already in the cabinet manual.
"I'm not intending to leave early but one should always be prepared", she said yesterday.
"I will continue to receive Cabinet and Cabinet committee papers".
Support is available through the Family Wraparound service which is a home-based family support programme delivered by family/whanau workers to help strengthen care for children, a new Family Start programme working with the parents of pregnant or very young children to help them understand and learn some child raising skills, and Pillars Family Pathway Centres in prison where families and whanau can visit the centre which is created to provide a child friendly environment conducive to strengthening bonds between the prisoner and their children.
Peters will remain in his offices on the Beehive's seventh floor rather than moving to Ardern's office on the Ninth Floor.
Ardern says the situation is no different from any other time the Prime Minister is away and the Deputy Prime Minister fills in.
Peters, who is Foreign Minister, has not scheduled any overseas trips while Acting Prime Minister.
"I may from time to time call the acting prime minister and he may at times chose to call me".
He will also fill in for Ardern at her weekly post-Cabinet Press conference on Mondays.
"I'm certainly hoping for the best, planning for the worst but expecting everything to be as we've set out".