Body Mass Index (BMI). Body Mass Index (BMI) is measure of body fat based on height and weight that applies to both adult men and women. BMI does not differentiate between body fat and muscle mass. Therefore, body builders and people who have a lot of muscle bulk will have a high BMI but are not overweight or obese.
The bump: or hematoma as we call it, can last for 1-2 weeks. Sometimes it gets slightly worse before it gets better. If the child is acting normally, and not vomiting uncontrollably, she should be fine. If she starts doing those things, call your pediatrician.
Becoming comfortable with the helmet. Most small children do not like wearing anything on their heads. It will likely take 3 to 7 days to get your child used to wearing the helmet for 18 to 22 hours a day. For the first few days, have your child wear the helmet as long as possible (half an hour to 1 hour).