Background: Since the American Academy of Pediatrics began its “Back to Sleep” campaign, the incidence of PP has increased. To aid prevention and management of PP, we compared perinatal histories of male and female infants with PP. Methods: 774 records of infants seen at our institution between 1998-2003 for abnormal head shape were reviewed. Only otherwise normal children with isolated PP based on clinical exam with or without radiographs were included (n=89). Gender distribution was assessed using chi-squared analysis. Sex-based differences in birth weight, maternal age, length of gestation and mode of delivery were assessed using independent sample t-tests and Fisher’s exact test. Demographic characteristics of births in Oregon between 1998-2003 were also compared. Results: The incidence of PP in boys (n=63) is more than twice as high as in girls (n=26; p<0.01). Mean birth weight of male PP patients (118.2±22 ounces) is higher than females (103.2±20; p<0.05). Maternal age, length of gestation and mode of delivery were not statistically different between male and female PP patients. Conclusions: Male infants have significantly greater risk for development of PP. The incidence of PP is associated with birth weight and head circumference but not with gestational age or delivery method.