Julie Anne Genter - the Green Party Minister who's also running for the party's co-leadership - has announced she's pregnant.

She's made the announcement at her home in Auckland this afternoon.

Ms Genter says she's going to have to get an extra seat for the bike - referencing her campaign for better public transport systems in New Zealand.

Julie Anne Genter says she wants her baby to be able to walk and cycle to school safely - so she's got a big task ahead.

"It's my intention to continue working as long as possible before the baby's due, and after that, I'll be staying in Auckland for a couple of months."

Ms Genter says her partner Peter will stay at home to look after the child, while she keeps up her campaign for safer roads and better modes of transport for New Zealanders.

She's due in August, two months after the Prime Minister Jacinda Ardern gives birth.

Ms Genter says they've failed to have children in the past.

She says she lost two pregnancies over two years ago, and then was unsuccessful after that time, so this came as a bit of a surprise.

However, she says it's very welcome and exciting.

On social media, friends and rivals in Parliament have been tweeting their congratulations to Ms Genter.

Jacinda Ardern tweeted that it was very exciting news, while outgoing National Party leader Bill English also sent his congratulations.

Ms Genter's rival for the Green co-leadership, Marama Davidson, says she'll be like an aunty to the child.