It is never a good idea to drive with a full bladder. The damage that this can cause, in a serious accident, is well recorded. It causes a "hydraulic lock", and can rupture the bladder. And even in the unlikely event of that happening, can you imagine the embarrassment, on top of the other trauma, of wetting yourself while waiting to be cut out of your vehicle? Much better just to stop regularly. When my kids were small I could plot a route anywhere round Scotland, just by toilets my daughter would use!