I had really bad heartburn in my first two pregnancies and only my first baby had horrible reflux, number 2 was a dream baby. I didn't have anywhere near as much heartburn 3rd time around but have another baby with horrible reflux.

Incidentally all my heartburn seems to have correlated better with the old wives' tale about heartburn meaning a baby with lots of hair. My first 2 were extremely hairy and this baby just has a little bit of hair. I never heard that theory either until after DD1 was born when lots of people started asking me if I had heartburn. Sorry a bit OTT.