I've also heard this before and statistically it's correct - in that many studies have shown that there is a higher m/c rate among women who have no morning sickness as a group. BUT many, many women don't get it and have a number of perfectly healthy pregnancies with not a day of sickness at all (my mother is one - she never had it at all with either of hers, can't even recall feeling slightly nauseous). My two best friends also never had it.

For me my experience was that out of four pregnancies, the two I lost had no m/s and the two that went full term I was sick from 6 weeks.

There are so many other factors and there'll be plenty of posts on this thread from other women who had no m/s and had trouble free pregnancies so try not to stress about it!