New Zealand Prime Minister Jacinda Ardern gave birth to a baby girl on Thursday, becoming only the second female world leader to have a child while in office.

Ardern, 37, and her partner Clarke Gayford announced the birth of their first child in a post on Instagram, saying the baby was born at 4:45 p.m. local time and weighed 3.31 kilograms.

"Welcome to our village wee one," wrote Ardern in a caption accompanying a photo of the family of three. "We're all doing really well thanks to the wonderful team at Auckland City Hospital."

[Instagram jacindaardern]

Ardern, who had previously said she and Gayford had been having trouble coming up with a name, did not indicate whether they had reached a decision.

Deputy Prime Minister Winston Peters took over as acting prime minister early Thursday morning when Ardern arrived at the hospital, and will continue to consult Ardern on any "significant" matters of government during her six weeks of maternity leave.

Ardern and Gayford previously said they will not give any exclusive interviews or photo opportunities while Ardern is on leave.

Following the prime minister's return to work, Gayford -- a presenter on a New Zealand fishing program -- will be a stay-at-home dad.

New Zealanders have responded positively to Ardern's pregnancy and birth, with many well-wishers taking to social media to express their excitement.

"You're an inspiration," one Instagram user commented on Ardern's photo.

"So awesome for a world leader to combine motherhood with your other amazing work," another wrote.

Ardern took office as prime minister in October, becoming the youngest female head of government in the world. She is the second woman to give birth while serving as prime minister, after Benazir Bhutto, Pakistan's prime minister in the 1980s and 1990s.