I'm in the same situation with an invite a week before I'm due. It's DHs cousins wedding, we are thinking he will go (as long as I'm not in labour!) but not drink alcohol just in case. I may take DD to the ceremony only (if bub hasn't arrived) but lets face it - outdoor wedding in late Feb at 39 weeks gestation - hmmm uncomfortable! I think the bride and groom will understand completely if you decline.