You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Mean head circumference at bih is? and explain in detail?
Head circumference: Measured with a nonstretchable tape passing through the maximum point of occipital protuberance posteriorly and at a point just above the glabella anteriorly. If the head circumference is more than expected, always measure the both parents&; head circumference, for benign familial macrocephaly is common. At bih, it is around 34 cm. HC increases by 2 cm/month for the first 3 months, 1 cm/month for next three months and 0.5 cm per month for next 6 months. Ref: Ghai Essential Pediatrics, ninth edition. pg. no. 35.