I'll add to this, too: my flow has generally been on the lighter side, cramps has been mild and my two pregnancies were quite easy (started easily, there was nausea but no throwing up, I was really tired but generally not too bad). Childbirths were relatively easy and quick, too (still the most brutal and painful thing I've been through, but, relatively).

I wonder if anyone has done any reasearch of this matter. It'd be interesting.