Hi Suzanne, thanks for the reply.
Are you using the 2003 version? Not 2013? The 2013 chart can be build in GE CPN but it needs to be 6.96 SP2 at least. There is an infobyte on this. Unfortunately, Fenton chart cannot be used for term babies. GE has a licensing agreement with the author that it would be used as intended, i.e. for preterm babies only.
I found Intergrowth 21 initiative and one of their calculators
We are having Pediatric Committee soon, so hopefully they will look into this…