About miscarriage and caffeine? Unfortunately it's been awhile since I looked into it, due to our own issues with miscarriage. I did a quick look to find what I was thinking of and couldn't find it offhand only because there were so many studies to wade through. The study I was thinking looked at nausea timing and changes in consumption of caffeine, and found that the risk for miscarriage associated with caffeine was mediated by nausea, but specifically by the tendency for women without miscarriage to decrease their caffeine intake after morning sickness occurring when it usually does. Nausea later in pregnancy didn't seem to be related to miscarriage risk, nor did caffeine intake.
It looks like there are various studies coming to different conclusions about this though so maybe that was just one of many:
