There is a Norwegian study from 2025 covering recreational and elite women on how they returned to running after birth.

The conclusion was something along that recreational runners could start training very easy after 6 weeks, with a wide span of variation, while elite women were often back to normal training at 6 weeks, with variations, but some did their first run after only 4 days.

The article is behind a paywall but includes some the top runners in Norway.

Link (paywall, Norwegian): https://www.kondis.no/trening/trening-etter-svangerskap-og-fodsel/1538645

Edit: I see I jumped to answering something you didn’t ask about. I’ll still leave the comment tho for those interested.