According to pediatricservices.com, there are many reasons why we should prevent our kids from sitting out like this.
1. Orthopedic concerns. “W-sitting can predispose a child to hip dislocation, so if there is a history of hip dysplasia, or a concern has been raised in the past, this position should be avoided,” the website reports.
2. If muscle tightness is a concern, W-sitting can aggravate the situation. That is because W-sitting positions “the hamstrings, hip adductors, internal rotators and heel cords in an extremely shortened range. If a child is prone to tightness or contractures, encourage another pattern of sitting.”
3. W-sitting discourages hand preference or movements because of the absence of hip rotation. As he is already comfortable, the child will not be encouraged to reach items beside or behind him. He is only focused on what is in front of him.
“Children with internal femoral torsion may have a habit of sitting in a W position, or on their feet, rather than crossed legged. Some children will trip over their feet if they toe in excessively. There is not a delay in the normal development of sitting, crawling, and walking.”–Concordortho.com
The best thing to do about it is to keep your child from making it a habit of sitting like that. When she is still younger, you can dissuade her by changing her position and telling her to sit differently. It is really best if we observe our children closely especially when they are playing so that we will know how they are sitting.
In the past, Dindin seldom sat like this but recently, I noticed that she is doing it more frequently. The good thing is, she does not stay in one position for long. But just to make sure, whenever I see her sitting like that, I tell her to sit properly in a nice way and then she would straighten her legs.