Epidemiology of Positional Plagiocephaly in Children
Incidence and Prevalence
Significant increase over last 20 years: The prevalence of positional plagiocephaly has increased significantly over the last 20 years. Several decades ago, the prevalence was estimated to be 1 in 300 (14, 40). In 1992 the AAP Task Force on Infant Positioning and SIDS recommended that healthy infants be positioned on their backs or sides when put down for sleep (1). This “Back to Sleep” campaign resulted in a dramatic decrease in the incidence of SIDS, from 1.2/1000 live births in 1992 to 0.56/1000 in 2001 (2, 3, 35). However, a dramatic increase in the prevalence of positional plagiocephaly was subsequently noted after the Task Force suggestion.
Currently approximately 20% in infants at 2 months age: Many reports now suggest the 2-year prevalence may be as high as 29.5% (14). The prevalence appears to be age-dependent with most cases of positional plagiocephaly manifesting in the first months of life. Prevalence at 6–7 weeks is estimated to be 16–22.1% (44), at 7 weeks to 4 months 19.7–46.6% (14, 26), and by 2 years of age as low as 3.3% (14).
Condition of infancy: Positional plagiocephaly is typically diagnosed in the first 4 months of life. It is seldom observed after the age of 2 years (14, 44).
Male 1.3 times female: The prevalence of positional plagiocephaly has been found to be higher in males than in females, with two-thirds of reported cases from 1991 to 2002 being male. The adjusted odds ratio is 1.3 (26).
None noted: There is no clear association between prevalence of positional plagiocephaly and geographic distribution.
Soft skull: Positional plagiocephaly is thought to result from forces applied to the developing soft pliable skull. These forces can be applied in the prenatal or postnatal (typically from positioning) period, or both.
Uterine constraint: Any factor that results in uterine constraint can predispose an infant to development plagiocephaly (17, 27). Risk factors associated with intrauterine forces include primiparity, maternal age > 35 years, breech position, prolonged labor, assisted vaginal delivery, oligohydramnios, cephalohematoma, and male sex (5, 10, 11, 26, 27, 32, 34, 36, 38). It is no surprise that the risk of positional plagiocephaly in twins or plural births is higher than in singletons, with asymmetry noted in as many as 56% (22, 34).
Supine position and infant neck problems: Risk factors in the postnatal period include exposure to the supine position, lack of prone position or “tummy time,” and infant neck problems (16).
Relationships to Other Disease States and Syndromes
Torticollis: Positional plagiocephaly can be associated with torticollis or “wry neck” in as many as 1 in 6 cases. This may occur as a consequence of hemorrhage in the sternocleidomastoid muscle resulting in subsequent scarring. This injury to the muscle can lead to muscle shortening caused by persistent unidirectional positioning and limited neck motion (35). Although it is not clear if torticollis leads to or results from positional plagiocephaly, torticollis is important to recognize and manage as it can limit repositioning efforts if not addressed (16, 23).