1 in 5 babies develops a flat spot. Most resolve on their own. Positional plagiocephaly is very common and does not affect brain development.
Prevention: Tummy time when awake and supervised. Alternate the direction baby faces in the crib. Limit time in car seats and bouncers when not traveling.
Treatment: Most cases resolve with repositioning by 6 months. Severe cases may require a helmet, most effective when started between 4-6 months.