Head circumference and chest size measurements are often taken on newborns and infants by a pediatrician to measure growth levels and development. These growth milestones reveal healthy brain growth and development. While a slowdown in growth after several months is expected, failure to grow at a steady rate may be an indication of a more serious condition.
During the first week or two after a child is born, a healthy baby's head and chest circumferences will be nearly identical. According to Medline Plus, the difference between the two is no more than .79 inches. In addition, both of these measurements are nearly identical to the measurements of the abdomen of the child. During the first two months of growth, a healthy child's head circumference increases at a rate of .79 inches per month. After two months, this slows down to .59 inches per month for two more months.
Increased Head Circumference
Increased head circumference is a condition that results when the circumference at the widest part of your child's skull is larger than expected. This increase in head circumference has no correlation to chest size, leaving your child's head disproportionately larger than his chest size. While this is commonly a benign and hereditary condition, it can also be an indication of more serious medical conditions, including increased intracranial pressure, macrocephaly and potential bleeding of the brain. If your child's increased head circumference is paired with vomiting and irritability, it is best to contact a health-care professional immediately.
Chest Size Overtaking Head Circumference
According to the "Indian Journal of Pediatrics," a child between the age of 20 and 21 months should have a larger chest size than head circumference. This milestone indicates healthy growth, as well as an adequate diet, with respect to both liquids and solid foods. While the chest size of the child overtakes the head circumference at this age, it returns to a directly even proportion around 36 months.
Measuring the ratio between head circumference and chest size in infants and young children can also indicate a possible lack of nutrients and proper sustenance for the child. For a newborn and infant, the initial head circumference of the child is developing and growing at a higher rate than the child's chest. After several months, this begins to slow down. With proper nourishment, the body and chest size of the child should begin to increase at a higher rate. If this ratio does not start to even out after the first few months of the child's life, this may be an indication that the child is not eating or absorbing nutrients properly.