Pediatrics General 9b01ee36 Microcephaly is defined as A Head circumference < -3SD below the mean for age and sex B Head circumference < -2SD below the mean for age and sex C Head circumference below 10th percentile the mean for age and sex D Head circumference below 15th percentile the mean for age and sex High-Yield Explanation Macrocephaly : Head circumference > 2SD above the mean for age and sex