Yes, a baby swing can cause flat head syndrome if the baby spends all his day in a baby swing as the baby can't change his lying or sleeping position in a baby swing. Flat head syndrome, also known as positional plagiocephaly, is caused when your baby spends too much time lying on their back. This occurs not only while sleeping but also while they are in car seats, carriers, strollers, swings, and bouncy seats. To prevent the flat head syndrome from occurring, it is important to reduce the amount of time your baby spends with their head against a flat surface when awake, including car seats, swings, strollers, and bouncy seats.