It's true. Though it's not about leaving them outside for the night with only a dull knife with which to fight off the wolves. It's about leaving them in their prams outside for nap time. Obviously bundled up to keep warm during winter.

We're not really concerned about baby kidnappings here, so it's not uncommon to see prams with sleeping babies outside of cafes while the mom or dad is inside having some coffee.

Not a joke. When my daughter was younger and we were visiting the daycare (förskola) facilities around us to pick one, in one of them they didn't have a room for children to sleep indoors, they always slept outdoors (even in the winter). This daycare was very highly recommended.

Anecdotally, when my daughter was a baby and had issues falling asleep, all it took was to take her for a walk outside in negative (celsius) temperatures and it was like we gave her sleeping pills. It never failed.

I grew up in a different country, so this whole concept was alien to me and it was diametrically opposite to my instincts, but I have to say that I'm a believer now.

They're fremen: https://www.bbc.com/news/magazine-21537988

Here in Poland my mum used to make me sleep outside (on the balcony) when it was as low as -20°C outside. (Covered in lots of layers.) It’s definitely not just Nordics.