Is w-sitting a bad posture for toddlers?

Yes!: The negative effects of "W" sitting are numerous. This may cause orthopedic problems, delay of development of postural control and stability, and delay development of refined motor skills. It's use is strongly discouraged. Parents should be consistent and try to anticipate when a child is going to move to the "W" position. The child can therefore be repositioned.

Yes: This is a posture some, mostly young girls find easy to get into. Many may sleep this way. However, that places some stress on the angle of the upper leg as it enters the pelvis and can delay the transition from pigeon toe to normal posture. I encourage parents to ask their kids to cross their legs in front,like an Indian chief or use a chair. Over time they are no longer able to do it.