Arden had announced in January, three months after taking office as the world's youngest female prime minister, that she was expecting a baby with her partner, television fishing show presenter Clarke Gayford.
LONDON, ENGLAND - APRIL 19: JNew Zealand's Prime Minister Jacinda Ardern (L) arrives to attend The Queen's Dinner during The Commonwealth Heads of Government Meeting (CHOGM) at Buckingham Palace on April 19, 2018 in London, England.
'I think it's fair to say that this will be a wee one that a village will raise but we couldn't be more excited'.
"Thank you so much for your best wishes and your kindness", she wrote.
"The prime minister having a baby while in office is a symbolically significant moment for our country, women in particular, and sends an important message that caring for children is one of the most important jobs in the world", said Davidson.
The prime minister, who had been given a due date of June 17, only stopped flying to the capital on June 11. She also changed travel plans, saying she didn't want to "tempt fate" so close to the birth.
"The public has generally been supportive of the popular Ardern".
Pakistan's Benazir Bhutto was the first world leader to give birth in office, in Pakistan. Asked by reporters if she had made a choice, Ardern said the process was going "terribly", per The New York Times.
She will be off work for 6 weeks.
The deputy leader of the National Party, Paula Bennett, wished Ms Ardern well in Parliament this morning.
But yet again, New Zealand is a trailblazer in this respect - Ardern is the third woman to be the country's prime minister, following in the footsteps of Helen Clark and Jenny Shipley.
Technically, Ardern will still be in charge of the country and will continue to read cabinet papers during her absence.
Ardern became the leader of New Zealand's Labour Party in September and was elected prime minister a few weeks later.
Now proudly wearing the tagline as the first child to be born to a sitting prime minister, Bhutto's daughter Bakthawar B-Zardari took to social media to congratulate Ardern on the baby's arrival.