Deputy Prime Minister Winston Peters is now Acting Prime Minister.
The couple join the tens of thousands of parents each year who make that same mad dash to hospital.
In 2017, 59,610 babies were born in New Zealand.
Of those, 30,588 were boys and 29,022 were girls. Ardern and Gayford have not disclosed their baby's gender.
As to what name they'll choose, if they were to stick to what's trending in New Zealand their options are:
For a girl: Charlotte, Harper, Isla, Olivia, Ava, Amelia, Mia, Mila, Sophie, Emily.
And for a boy: Oliver, Jack, Noah, William, Hunter, James, George, Mason, Lucas, Arlo.
If born today Ardern and Gayford's baby would share a birthday with Prince William (who the couple met in Britain this year), actor Chris Pratt and singer Lana Del Rey. Their star sign is Cancer.
The child's birth will be significant: he or she is the first child born to a female New Zealand Prime Minister, in power, in our country's history.
Although this is a first for New Zealand, Ardern is not the first woman in power in recent times to give birth while running a country.
Former Pakistan PM Benazir Bhutto gave birth to daughter Bakhtawar on January 25, 1990, while she was in office.
Bhutto also had an older daughter two years earlier just a few weeks before she took office in December 1988.