Average head circumference at birth is-
Head circumference

Head circumference is measured from the occipital protuberance to the supraorbital ridge of the forehead which is the maximum occipitofrontal diameter of the skull.
The head circumference in utero grow by 0∙5 cm in first 2 weeks, 0∙75 cm in 3rd week and after that 1 cm/week till birth.
The average head circumference at birth is 35 cm, which becomes 40 cm at 3 months, 43 cm at 6 months, 46 cm at 1 year, 48 cm at 2 years and 52 cm at 12 years.
Head circumference is important to add to the diagnosis of neurological dysfunction and microcephaly.
Microcephaly is defined as a head circumference that measures more than three standard deviation below the mean for age.
Macrocephaly is defined as head circumference that measure more than two standared deviation greater than mean for age.
35cm
40cm
45cm
50 cm