Pediatricians maintain growth charts to track physical development. For the first 36 months, your pediatrician notes your child's height, weight and head circumference; then, head circumference is no longer tracked, but body mass index, or BMI, is. Measurements are converted to percentiles to track size and growth in comparison to other children of the same sex. The percentile isn't necessarily important, though. Mostly, your pediatrician watches whether your child's growth occurs in healthy patterns. At first, measuring your baby's height from crown to heel at regular, frequent intervals helps you and your pediatrician monitor growth.
Enlist a helper to assist with taking your baby's height measurement. For accuracy's sake, you'll need at least one other person to hold and position your child while you take the measurement.
Lay your baby down on her back on a hard, flat, elevated surface. A changing table or clean and clear kitchen counter works well.
Instruct your helper to gently straighten your baby's legs so her knees are flat on the table or counter. Your helper should also prevent your child from arching her back. If possible, or if you can get a second helper, your baby should ideally be looking straight up at the ceiling, too.
Run a tape measure right alongside your baby, with one end at her heels and the other going to the crown of her head. Don't wrap the tape measure down over the curve of her head or otherwise have it not running straight. The length shown is your baby's height.