Is there some indication that morning sickness is related to ingesting harmful toxins, now or in the evolutionary past? It doesn't seem from my experience (close second hand only) that morning sickness is more than increased sensitivity to certain foods, and rather a general nausea that makes many nutrious foods difficult to keep down.

"You would have to skip a lot of meals to equal one bad poisoning episode."

Such as one or two a day for 2-3 months?