This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Average head circumference at birth is- 
Select and explain. 
A. 35cm, B. 40cm, C. 45cm, D. 50 cm
A: 35cm
Answer: A: 35cm 
Explanation: 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.