Head circumference from birth to age 48 months for infants in Sweden

Aim: To describe the development of head circumference, from birth to age 48 mo, of infants in Sweden. Methods: Every infant born on the 15th of any month in the 1981 birth cohort, living in Sweden as of 31 December 1989, was studied from birth to age 48 mo ( n =3158). By collecting data from child healthcare records and then analysing these data using piecewise linear regression, means and other statistics were produced for every age. Data were analysed for all and with exclusions for low birthweight and those born outside Sweden. Results: From the sample of 3158, data for 3107 infants were collected, making the percentage of missing individuals 1.6%; thus, non‐response bias is minimized and high national representativeness is achieved. Summary statistics for head circumference are presented. Comparisons are made to international reference materials, and to previous and current Swedish reference curves. Conclusion: For the first time in Sweden, and without selection bias, means and distribution of head circumference measurements are documented longitudinally for a nationally representative sample of infants.