Wellington (Web Desk): New Zealand Prime Minister Jacinda Ardern is set to become the second premier in recent history to give birth while in office — the first being former PPP leader Benazir Bhutto .

BB gave birth to her second child as PM in 1990 - in what was reported to be a first for an elected leader, rather than royal families.

Ardern said she and her partner, Clarke Gayford, were expecting their child in June, after which she planned to take a six-week break.

"And we thought 2017 was a big year!" she wrote on Instagram.

She said she aimed to be “contactable and available” during the period and would resume all leadership duties when it was over.

Ardern , who did not reveal whether she was expecting a boy or a girl, said she and Gayford previously had doubts they could conceive.

“Clarke and I have always been clear we wanted to be parents but had been told we would need help for that to happen,” she said. “That's made this news a fantastic surprise.”

Ms Ardern became New Zealand's youngest prime minister since 1856 when she formed a centre-left coalition in last October.