Updated at 8.50am

New Zealand prime minister Jacinda Ardern has given birth to a baby girl.

Ms Ardern posted a photo on her Instagram account showing her and partner Clarke Gayford with the baby at Auckland City Hospital.

She wrote that she was feeling very lucky to have a given birth to a healthy girl, and that their daughter arrived at 4.45pm (NZ time) weighing 7.3lb.

She thanked everyone for their kindness and said they were all doing well, and also thanked the team at the hospital.

The 37-year-old Ardern is the second elected world leader in modern times to give birth while in office, after the late Pakistan prime minister Benazir Bhutto gave birth to daughter Bakhtawar in 1990.

Ms Ardern's due date was June 17.

The birth has been highly anticipated in the South Pacific nation of nearly five million people.

Deputy prime minister Winston Peters is acting prime minister.

Ms Ardern plans to take a six-week leave before returning to work.

Under the arrangement, Ms Ardern will still be consulted on major decisions, including issues of national security.

Ms Ardern has said she is confident the government will continue to run smoothly in her absence.

Asked earlier this month how the couple had been faring while trying to choose a name, Ms Ardern responded: "Terribly. Do you have any suggestions?"

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