Prime Minister Jacinda Ardern has spoken to the public for the first time since leaving hospital after the birth of her child a week ago.

She posted a livestream of herself, holding baby Neve, on Facebook and talked about the Government's families package, which came into effect today.

In the video she can be seen sitting on the couch at her Sandringham home, holding Neve in a blanket on her lap.

"Today is the day the families package comes in... couldn't help but share a few thoughts from the couch!" Ardern posted on her Facebook page.

Families with newborn babies would be up to $60 better off a week, she begins to say in the video.

"It's really an acknowledgement about that being such an important period.

"Best start - I am so, so proud of.

"From that time that it was designed on the floor of my friend's home in Hastings, we tested it with a lot of people, worked it through, and it stood the test of time.

"I think the principle behind it is really, really solid."

Everyone who was receiving Working for Families would receive more, she said.

The Families Package, which was funded by cancelling the previous National government's planned tax cuts, will cost $5.53 billion over five years.

The Government estimates that by 2020/21, when the package is fully rolled out, some 384,000 families with children will be better off by about $75 a week. It is projected to lift the number of children living out of poverty by 64,000, or about 41 per cent, by 2020.