Overall hip, shoulder and back flexibility is needed for the cradle. Hardest part is finding the correct amount of pull and push to balance this pose. I’ve noticed students with shorter torsos have the most difficulty.
All contortion poses can be broken down into relevant progressions. Take a look at the regressions that are relevant for this pose. If you’re working towards the current pose, mastering these below will help you on your way.
If you’ve mastered this pose take a look below for more advanced variations