Wellington, Jun 21 (IANS): New Zealand Prime Minister Jacinda Ardern gave birth to a baby girl on Thursday, the first world leader in nearly 30 years to have a child while in office.

In a post on her official Instagram account, Ardern said the baby arrived at 4.45 p.m. and weighed 3.31 kg, CNN reported.

"Thank you so much for your best wishes and your kindness. We're all doing really well thanks to the wonderful team at Auckland City Hospital," she said in her post.

Ardern, 37, was admitted to the hospital earlier in the day. Her expected due date had been June 17.

She was elected in October and had announced her pregnancy in January via Instagram.

"Clarke and I are really excited that in June our team will expand from two to three, and that we'll be joining the many parents out there who wear two hats," Ardern said in the post.

Excitement and anticipation had been building over the last few days, with many media outlets setting up live blogs to track the latest developments.

Jessie Chiang, a New Zealand Radio reporter, tweeted that she and other journalists had been at the hospital since 6 a.m. "No baby yet...but they are feeding the media," she wrote.

Another outlet even put together a baby-themed playlist to "help bring her bub into the world".

New Zealanders also speculated over the baby's gender and name. One Twitter user joked on Thursday: "If it's a boy I'm going with Winston Michael Joseph Peter Norman David David David Phillip Andrew Gayford Ardern."

However, the baby has a higher chance of being named Oliver or Jack -- the two most common baby boy names of 2017. If it's a girl, it might be Charlotte or Harper, the most common girl names, the CNN said.