Ms Ardern, 37, arrived at the country's largest public hospital at 5.50am local time on Thursday with her partner Clarke Gayford, her spokesman said.
"I'll be prime minister and a mum", she said on Facebook, adding that her partner Clarke Gayford, who hosts a television fishing show, would be a "stay-at-home dad".
Ms Ardern later shared the same photo on her Instagram account, and it quickly amassed tens of thousand of likes.
She is thanking the nation for best wishes and kindness - and says she is doing well thanks to the team at Auckland City Hospital. Pakistan's Benazir Bhutto gave birth while she was prime minister in 1990.
"Only later did I learn that I was the only head of government in recorded history actually to give birth while in office".
However, she said she would remain in charge by continuing to read cabinet papers during her time away.
Ardern has fielded several questions about whether she wanted children, but has told media outlets that she should not have to respond to such an inquiry.
"I am not the first woman to multitask".
Jacinda Ardern handed over the reins to her enigmatic 73-year-old deputy Winston Peters after arriving at Auckland Hospital on Thursday morning.
Ms Ardern will share news of the birth herself - most likely through Instagram like she did the pregnancy bombshell - which will the be followed by a formal government announcement.
She said that after the birth, she hoped to have some quiet time to enjoy as a family.
Political parties have been quick to acknowledge the news, with National leader Simon Bridges congratulating Ardern.
Former prime minister Helen Clark tweeted it was "a proud day for Jacinda & Clarke & for us all". She is expected to take leave for 6 weeks. "Plenty of women have multitasked before me, and I want to acknowledge that", she said when revealing the pregnancy in January. "But I think it is going to inspire a lot of women".
On this day, which is dedicated to the inner and outer well-being of human body, people across the world practice yoga in groups. While Narendra Modi performed yoga in Dehradun , leaders and politicians across the country hosted similar events.
The Hornets will get the Nets' second-round pick Thursday night (45th overall) and a second-round pick in 2021, the person said. He averaged 16.6 points, 12.5 rebounds, and 1.6 blocks in 30.4 minutes per game, and shot 55.5 percent from the floor.
Fox's board said it still has the right to weigh competing offers, signaling that the bidding war for its assets could continue. In order to sweeten the pot for their 21st Century Fox bid, Walt Disney has upped their initial offer once again.
Cisse has been the Senegal manager for three years, leading the African nation to their second World Cup finals in their history. And then Senegal fans, after their Lions upset Poland, 2-1, followed suit.
Morocco coach Herve Renard is expecting Portugal to give his side a tougher game than they had against Iran. And he claims there is no reason why the 33-year-old could not play at the next World Cup in Qatar in 2022.
The Supreme Court overrules the Quill case, which previously set the precedent for collecting sales tax from online sellers. South Dakota was backed by 35 states in the case, each of which filed an amicus brief in support of online sales tax.
The most controversial aspect of Canada's move has been setting the minimum age for use at 18 or 19, depending on the province. The Senate voted 52 to 29 in favor of a revised bill from the elected House of Commons, and there were two abstentions.
The 47-member council has a number of powers, including the ability to establish panels that probe alleged human rights abuses. Critics say this sends a message that the administration turns a blind eye to human rights abuses in some parts of the world.
Non-OPEC members including Russia, Oman and Mexico also agreed to cut 558,000 bpd off their production to stabilise the market. Indeed, the single largest factor that could push prices down going forward would be a sizable increase in OPEC plus supply.
But Beijing's mention of "comprehensive measures" suggests that it would go beyond tariffs , said Jake Parker of the U.S. The tariffs on Chinese imports are the latest in a spate of protectionist measures unveiled by Trump in recent months.
Alli remains a doubt for Panama clash
The Red Devils were kept at bay in a niggly first half before Dries Mertens opened the scoring within seconds of the re-start. They try and shoot themselves in the foot [at] every World Cup they go to.
Kim, Xi agree on resolution of key issues
This is the missile test engine site that Trump had mentioned after their meeting, though at the time he did not name it. This suggests that agriculture and railways will become key parts in North Korea-China economic cooperation.
Dustin Johnson Majors: Has DJ Won One?
Open, The Associated Press reported erroneously that his winning score of 281 was 13 shots higher than previous year . It was definitely more receptive this morning than yesterday, that's for sure.
As Kim visits China, Xi flaunts bargaining chip in trade dispute
On Tuesday, the USA and South Korean militaries confirmed they have called off scheduled joint exercises following Trump's order. As NPR's Anthony Kuhn notes, Chinese state media have even publicly announced this third visit with Kim still in the country.