Although the pumpkin plants in my garden are huge they keep producing little baby pumpkins that just fall when about the size of a tennis ball.
A friend of mine has suggested it is casued by the fact that they have not germinated. The cure?
Get a flower (that has no bulge under it)
Wipe the stamen over the flowers on top of the little pumpkins
I have now tried this – wait and see I guess!