Here's how growth charts work: Doctors plot the baby's measurements on the chart to get a percentile. The percentile shows how the baby is growing compared to other babies of the same age and gender.

Clinics use growth charts to map a baby's growth up to 5 years. In South Africa, you would've received the Road to Health booklet or card with your baby's birth weight and length plotted on the graph.

The current standards for infant growth were published back in 1977 and based on a limited survey of babies born in Yellow Springs, Ohio, between the 1920s and mid-1970s.