Most toddlers will develop some degree of bow-legged ness regardless of which type of carrier is used. The Mei tai I am not familiar with (of course, the Mai Tai is a different story!). Babies typically are born bow-legged, and remain that way for over a year. Usually the legs start to straighten-out and are mostly straight by 18 months. After this, the legs start to get knocked-kneed and progress this way for the next few years. Finally, they become straight again by adolescence. There are some red flags to watch for: Asymmetry, short stature, or if the child is extremely knock-kneed.