Since it is said that vomit contains acid, is morning sickness harmful to a expecting woman?

It is true that emesis does contain HCl or hydrochloric
acid from the stomach. Periodic morning sickness or nausea and vomiting are fairly
common in the pregnant female but these episodes are not harmful unless they become
intractable. Intractable nausea and vomiting means that the nausea and vomiting episodes
are continual and prolonged. In other words, the female has continual nausea and
vomiting with repeated episodes.

With intractable nausea
and vomiting, the danger comes from the loss of electrolytes in the emesis, not from the
HCl coming into contact with the esophagus or mouth. Repeated episodes of vomiting or
diarrhea cause us to lose fluids and electrolytes like Na., K., Cl., etc., this can
become harmful in the pregnant or nonpregnant female.