Some help with my pumpkins please???

Hello All,
Pumpkins seem to finally be growing (touch wood) although I only have one on each plant, but its better than none lol.
I have one massive plant that seems to be taking over the garden, one stem has worked its way half way across the garden this is one with a pumpkin on it though, I have been advised to trim the stem back to help make the pumpkin grow but not sure if I should?!?!?!?
Lucy x

 

Hi Lucy, what do you mean by trim the stem back?