The change in customised centile between 28 weeks and 36 weeks (A) and 28 weeks and birth (B) was calculated as the later fetal weight centile minus the earlier fetal weight centile.

A fetus slowing in growth will thus have a negative number to describe their weight centile change; a fetus that maintains growth will have a change of zero, and a fetus with an increase in growth will have a positive number to describe weight centile change.