My RE sent me to the ER. It was a bit inconclusive, but they thought an irritated cervix due to progesterone.
I am 23 wks now and nothing since that one episode.
FWIW, I have one latte each day (with only one shot of espresso). I struggled through many OE IVFs and one DE without any caffeine and felt like I was sleep walking the whole time. My OB's guidelines say roughly 2.5 shots of espresso a day is OK...I just choose to cut it back to one a day.