Former New Zealand Prime Minister Jacinda Ardern has delivered a final speech as a politician to parliament, reflecting on her five-year tenure as prime minister.

Ardern stepped down as prime minister in January, saying she no longer had "enough in the tank" to lead the country.

In her parliamentary address on Wednesday, Ardern said she had a failed round of in vitro fertilization when she became the leader of the Labour Party.

She said she thought she wouldn't become a mother and campaigned to become prime minister, but got pregnant "a couple of" months later.

Ardern took office in 2017 and gave birth the following year. She became the world's first-ever sitting prime minister to take maternity leave.

She wrapped up her speech by encouraging others to take office, saying they can lead just like her even if they are anxious and emotional, whether or not they are mothers.

Ardern will formally resign her parliamentary seat this month.

She will work as a special envoy for an organization jointly established by tech companies and nations to combat online extremism. The project was launched after mosque terror attacks in Christchurch in 2019.