For newborns, the best way to carry them is tummy to tummy (upright). Cradle carry is discouraged because of the risks of hip dysplasia which is the general instability or looseness of the hip joint. Click here to see an animated video of how hip dysplasia happens and here for the different stages of hip dysplasia. Here's a photo of the proper position of a baby inside a sling to prevent hip dysplasia.
|from the International Hip Dysplasia Institute|
Another reason why cradle carry is discouraged for newborns is because of the risks of positional asphyxiation. The BabyWearing Institute defines positional asphyxiation as follows:
[Positional asphyxiation] is essentially a kink in the airway. Baby's chin hits his chest and kinks the airway. Baby cannot breath and dies within 3-5 minutes without making a sound. Baby's head is too heavy for him to lift out of a compromised position like the cradle carry.
If your baby prefers being in the cradle carry position in your arms without a carrier, it doesn't mean that you should put the baby in a cradle carry position in the carrier. As this post explains, without a carrier, a baby carried in his/her parent's arms will get shifted about A LOT. Baby will not be in the cradle position for a long time.
Babywearing Safely: Introduction
Why Cradle Carry is discouraged
Front Facing, Front Carry?
Legs Out Position