14What Causes Plagiocephaly?
Positional plagiocephaly usually occurs when a baby lies on his back or with his head to one side for an extended period of time. Babies that are really good sleepers (or that have really large heads) may develop plagiocephaly because they don't/can't move their head around much when
they sleep. Babies that spend a lot of time on their back in swings and car seats can also develop plagiocephaly from being in one position for so long.
It's rare but sometimes babies can begin to develop plagiocephaly in the uterus. Babies that are born prematurely are sometimes more likely to develop plagiocephaly because their skull bones are softer than a full term baby's skull. Also, when there are multiple babies in the womb and babies have less room, they may be cramped in the uterus. If the mother has an unusually shaped uterus or fibroids in the uterus, these situations can also cramp the baby.