What is normal head circumference for a 9mnth old?

Depends on gender ;: Velocity of growth. Has the head circumference grown normally along a single curve between 5th-95th%ile or increased too rapidly, e.g., jumping from 25th to 95th %ile (as may be seen in autism or hydrocephalus), or too slowly, e.g., dropping from 25th to 5th%ile, (indicating insufficient brain growth)?Girls' range at 9 months is 41.6-46.6 cm; avg. Is 44 cm. Boys, 43-47.4 cm; avg. Is 45.4 cm.