Baby’s heads are very soft and malleable for passage through the birth canal and for brain growth in the first few months. Thus it’s easy for their head’s shape to flatten from laying on one side too much. They won’t develop the ability to use their necks for a few months.
Flat head syndrome occurs when a baby spends too much time on one side of their head, be it the back or sides. Some infants naturally tend to find comfort laying in the same spot. It can also occur if your baby spends a great deal of time using things like a car seat or rocker.