In my personal experience, I found the morning sickness was an indication of
a health pregnancy.  My first pregnancy, no morning sickness and I
miscarried.  The next two, felt like I was hungover for 3 months with both!
Both were healthy babies!  With one I craved healthy food - especially
chicken broth/soup.  The other, I swore she would come out a ho-ho (yes, this
was all pre paleo).  My doc related anecdotally that he had see many
situations like mine (morning vs no morning sickness, different cravings with
different kids).  And of course, he had see pregnancies to to the contrary.
So, as with everything concerning the human body, there seems to be no one
generalization you can make  : )