Plagiocephaly and Torticollis:
The American Academy of Pediatrics has recommended that babies sleep on their back in order to reduce the risk for Sudden Infant Death Syndrome.
While that recommendation has made an impact on the number of children affected with SIDS, it has also caused a big increase in the number of flat head that we are seeing. That condition is called plagiocephaly, and the muscular condition is often occurs with, and probably because of, is torticollis. Both plagiocephaly and torticollis have other causes.
One common cause is likely the position the baby has in the womb. As kids approach term in the womb, they are squished in a pretty small space. They probably find a position which is most comfortable for them, often tilting their head to one side or another. When we had the kids sleeping primarily on their stomach (which is very much frowned on now), they needed to symmetrically use their neck to lift their head Now, while lying on their back, they often tilt their head to the side that was comfortable in the womb.
If they keep that head tilt, the sternocleidomastoid muscle ( the long ropey muscle that goes from about your jaw to your collar bone) on one side gets longer, because it's stretched. The other side gets short, because it's not being stretched. It eventually loses its normal range of motion and becomes very hard to stretch. The kids often keep their head turned away from the side that's shorter. Muscle shapes bone. The head tilt shapes the muscles which then flattens the bone.
The shortening of that neck muscle and the resultant head tilt is called torticollis. Torticollis can have other causes, including a congenital form. If it is muscular torticollis, then repositioning and stretching exercises help.
We hear about "tummy time" being a way to prevent this, but Tummy Time sounds like this big production, so I've started to call it "get off the back of your head time" meaning hold the babies, maybe use baby carriers, but do something so that the pressure placed on the bone stops.
If that doesn't help, usually by 4 months of age, physical therapy may help and if therapy doesn't change the head shape, then using a helmet of some sort may help.
DOC band supplier http://www.cranialtech.com/clinic/wi.html
Physical therapy: Torticollis clinic at Children's Hospital of Wisconsin