its not ideal but shouldnt have too much negative effect I would assume, pruning too early can be much more problematic.
If your buds have swollen and ready to burst, or have started to burst just be careful not to damage the buds you want to keep.
Downside is the sap in the vine will have started to flow so you loose the carbohydrate stores that have been used to get the rest of last years growth going...but thats the the way the cookie crumbles.
Go and do it now if you are going to do it. Sooner the better!!!
If in doubt consult a good book, "Viticulture" by coombe and dry (Vol 2, proceedures) should be able to answer your question.