The scientific literature specific to infant carriers is limited and does not specifically address hip health. However, there is a great amount of scientific understanding about harmful hip positions for infants. The harmful effects of unhealthy positions have been shown in humans by traditional swaddling practices. Cultures that practice traditional swaddling have seven to ten times more hip dislocations than cultures that have stopped those practices. Harmful hip positioning has also been demonstrated in rabbits, pigs, and rats. Some of the scientific literature for this is cited in our explanation of the IHDI swaddling statement. [https://hipdysplasia.org/for-physicians/pediatricians-and-primary-care-providers/]
With regards to infant carriers, there have not been any scientific studies that specifically evaluate modern baby carriers. However, there is research that shows healthy hip development and low rates of dislocation in cultures that carry their children on the mothers’ bodies with the hips bent and spread in the “frog-squat” position. This is also known as the “jockey”, or “M” position. Keeping the legs in this position as treatment for newborn hip instability has been shown to improve hip development during infancy and early childhood. There are hundreds of scientific studies supporting this position and none making a case against it.
Thus, we know the most harmful hip position and we know the most beneficial hip position during early infancy. Approximately one in six infants have hip instability at birth. Thus, it is logical to stay away from the most harmful position and encourage the best position whenever this is practical and possible.
From Charles T. Price, MD, Medical Director, IHDI