(CNN) New Zealand Prime Minister Jacinda Ardern gave birth to a baby girl 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 pm local time, weight 3.31 kilograms (7.3 pounds).

"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.

Admitted to the hospital earlier in the day, Ardern's expected due date had been June 17.

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