Makena shot a day late-- few questions

Emily
Ok so I've been on the Makena injections for awhile now, I'm 33 weeks and stopping them at 36 weeks. I have a few questions. First, I'm supposed to get the spot today, because Tuesday's are my day, but I have an ob appointment tomorrow and was just going to wait until tomorrow so I don't have to go twice. Will this be an issue?
Also, do you go into labor after your last shot, since your body will have a drop in progesterone?