Growth charts are a way of tracking your baby’s growth. Basically, they plot your baby’s measurement in comparison to other babies of the same age. For example, if we lined up 100 babies based on their weight, the percentage shows where your baby would place in this line-up. 56 percentile for weight-for-age indicates your baby is larger than 56% and smaller than 44% of babies of the same age. However, these charts are not intended to be used to compare your baby to other babies. This is not a test where a higher percentage is the goal. Achieving 100% is not the purpose of growth charts. Instead it is a way of tracking your baby’s growth and comparing her to herself. At 3 months, is your baby still around the 56% like they were at 2 months? A sudden drop or a rapid jump of 2 percentile groups can be a red flag and should be looked into; for example: dropping from 56% to 8%. Consistency is the important aspect regarding growth charts.
There are two common growth charts that are used: The Centre for Disease Control (CDC) charts and the World Health Organization (WHO) charts. The difference between the two is more than the names. The CDC growth charts are base on formula fed and combination (breastfed and formula) fed babies. The WHO growth charts are based of exclusively breastfed babies. This difference is important. Exclusively breastfed babies grow differently; weight gain tends to be quicker in the first few months but typically slows down around 4-6 months. Around a year old, exclusively breastfed babies tend to weigh less than a baby that was fed exclusively formula. A baby fed breastmilk grows the way nature intended and is the biological norm for growth. It makes more sense to use the growth charts based on the biological norm. If it does seem like your baby is slowly dropping percentiles, it is worth looking into to see which growth charts are being used.