I do not cut mine as they have plenty of space to grow and that removes one chore out of my "to do list". If there was a reaon for pruning them then the answer is... it depends on what kind of hydrangeas they are. Do you know? There are hydrangea macrophyllas, arborescens, asperas, serratas, paniculatas, quercifolias (aka, oakleaf) and others.
Macrophyllas, asperas, oakleafs, serratas, they all produce invisible flower buds in July-August. If you prune those types of hydrangeas now, you will effectively be cutting off this year's blooms because the majority of the buds are at the end of the stems. But if they are rebloomers, yes, you will only be cutting off early Spring blooms and you will still get bloomage later on, probably around June-July 2014.
I would let macrophyllas, asperas, oakleafs, serratas bloom, enjoy the blooms and then prune at the end of June 2014.
The ones that produce blooms in the Spring are arborescens and paniculatas. I am not sure those (if yours are those) have gotten to the point of producing flower buds yet (the leaves fully develop before the flower buds do). If so, you can prune them now.