My son loves to sleep turning his head to the right and at 2 months old he developed flat spot (plagiocephaly head shape when one of the sides at the back of the head is flat-there are 2 more flat spot shapes: flat back and flat both sides of the head). I bought this head support because of the great reviews.
At first I wasn't happy because it says that it can not be used for sleep, but since he can't change position by himself. Also I use it in a bouncer and car seat (works great in Chicco Keyfit 30), and for tummy time which is great for arms support. So during the night my son sleeps always on the back on Boppy head support, and during the day on the sides (I alternate sides to maintain good head shape). The boppy head support doesn't bother my son at all.
If you suspect that your baby's head has a abnormal shape talk to your doctor or you can make assessment at home:
1-from the bird's eye view normal head shape is 1/3 longer than it is wide,