Jacinda Ardern, the Prime Minister of New Zealand, has given birth to a girl. Her first child was born weighing 7lb 3oz at Auckland City Hospital on Thursday.
The 37-year-old has become only the second elected world leader to give birth while in office.
"I'm sure we're going through all of the emotions new parents go through, but at the same time feeling so grateful for all the kindness and best wishes from so many people. Thank you," Ms Ardern said in a statement.
She added that both mother and daughter are doing well, as she praised medical staff.
Posting a picture on Instagram with her partner Clarke Gayford, 40, and their new baby in hospital, Ms Ardern said she was "feeling very lucky".
Deputy Prime Minister Winston Peters has now taken over as acting prime minister.
However, she said she would remain in charge by continuing to read cabinet papers during her time away from office.
The leader plans to take six weeks of maternity leave before returning to work.
Such is her dedication to work that Mr Gayford, a television presenter, posted a picture on Twitter of Ms Ardern continuing to read official papers in the hours before she gave birth.
Ms Ardern, who was elected in October, revealed in January that she and Mr Gayford were expecting their first child.
The first world leader to give birth while in office in modern times was Benazir Bhutto, the late former Prime Minister of Pakistan, in January 1990.
But Ms Ardern previously downplayed the significance of having a baby while in office.
"Lots of people juggle a lot of things in their personal and private lives, and I'm not unusual in that," she said. "Plenty of women have multitasked before me, and I want to acknowledge that."
Video: Jacinda Ardern announcing her pregnancy
The birth capped an eventful year for Ms Ardern who became prime minister, three months after inheriting the leadership of the Labour Party when it was languishing in the polls.
Congratulations quickly flooded in from around the world and across the political spectrum, with New Zealand opposition leader Simon Bridges among those to offer his congratulations.
"Being parents is a joy and a privilege and we are sure your new arrival will fill your lives with all the happiness our children have ours," he said.
And Helen Clark, New Zealand's first woman prime minister from 1999 to 2008, said it was "a proud day ... gender quality in action".
Congratulations to @jacindaardern & @NZClarke on the birth of their daughter ����today. What a proud day for Jacinda & Clarke & for us all. New life, new hope. Parenting arrangements are #genderequality in action. This is 21st C NZ. #ProudKiwi ���� https://t.co/w52w8CJLSJ— Helen Clark (@HelenClarkNZ) June 21, 2018
Ms Ardern has said she plans to return to work at the beginning of August.
Then, Mr Gayford will take care of the baby and will travel with his partner between their Auckland home and the capital, Wellington, as well on international engagements.
Ms Ardern worked until late into her pregnancy, regularly encountering members of the public who touched her stomach and passed on gifts.
"It's been great," she told reporters at her last major public event before giving birth. New Zealanders are incredibly generous people and have been generous in their support of me regardless of the politics just as another human being going into a new stage of life."
Video: Election of New Zealand's second female leader
Ms Ardern's plans for a family had sparked a sexism row during the election when a television host quizzed her on the issue, saying voters had a right to know before they cast their ballots.
She rejected the line of questioning as "unacceptable", saying pregnancy and child rearing should not hinder women's opportunities in the workplace.
"It is a woman's decision about when they choose to have children and it should not predetermine whether or not they are given a job or have job opportunities," she said then.