When treating plagiocephaly, parents are instructed to keep their baby off of the flattened spot as much as possible to prevent worsening. Often, parents translate this to keeping the baby upright as often as possible with no pressure on the head at all in hopes that this will round out the head shape. One frequent question I field in my practice when dealing with babies who have plagiocephaly is, "If I just keep him off his head, it will round out?" It would seem a logical solution, but in fact, allowing the baby to lay on the rounded area is actually more beneficial. The brain grows in the path of least resistance, therefore, if you put pressure on the right side, the brain "moves" left. The scenario I use for parents is this: think of a tennis ball in a water balloon. If you put pressure on one side of the balloon, the ball shifts to the opposite side. When the soft spot and sutures are still open, the head is very much the same way albeit not as pliable. Therefore, placing the baby on the rounded part of the skull actually acts to shift the head to a more rounded position. This is same concept of cranial remolding helmets. These orthotics hold the high points (rounded parts) of the skull and take all pressure off of the flattened areas to encourage brain growth in the desired direction, simply put. Conservatively, placing the baby's head on the rounded area follows the same concept.
In addition, according to Wolf's law, bone will adapt to the load placed on it and actually make structural changes to become stronger the more load it is experiencing. In essence, the skull gets stronger by having the baby lay on it. This is important in protecting the brain making lying on a firm surface essential. Prolonged lying on soft surfaces will thwart this process of strengthening of the bone.
Once the soft spot and sutures of the skull close, the head shape will remain unchanged for the most part. Eighty percent of head growth occurs in the first year of life making this the perfect window of opportunity to ensure a nice rounded head for the future. The best practice is to place your baby a variety of positions on a firm surface for a rounded and strong skull. If high points or rounded areas exist, think of the path of least resistance and encourage the baby to lay on those areas of the head.