I don't think this has been brought up on here before, but this is a snippet from an article on MSN about
problems that coffee can cause certain people:
You may want to give up coffee if you're pregnant (some equivocal evidence suggests that caffeine may trigger miscarriage); have trouble sleeping (caffeine is a stimulant); or have heartburn or gastroesophageal reflux disease ("Caffeine loosens the valve at the end of the esophagus and can allow for the backwash of stomach acid," explains gastroenterologist David H. Robbins, MD, of Beth Israel Medical Center in New York City).