Back in early 2016, I was looking into molybdenum and noticed that a regional diet study had found lower morning sickness in areas where the diets were high in legumes and whole grains, which happen to be the best commonly-eaten food sources of molybdenum (element #42). The grains that are high in molybdenum are oats and barley, not wheat, which would explain why this connection hasn't been made before. Molybdenum is used by five known enzymes in the body, one of which is sulfite oxidase. Sulfite oxidase, which converts sulfite to sulfate, catalyzes the final step in the process of breaking down endogenous (made in the body) hydrogen sulfide all the way down to sulfate (which is recycled or excreted in urine). Sulfites are known for making people sick, including with nausea, and recent research into hydrogen sulfide has found that it's important to angiogenesis (making new blood vessels from existing ones, so very important when the placenta is being formed) and keeping the uterine muscles from contracting. It looks as though morning sickness might be partly a result of excessive sulfite in our bodies due to not being able to break it down fast enough. Foods that interfere with sulfite oxidase (sulfites and nitrites, especially) do seem to be common triggers for nausea in morning sickness and motion sickness.
So to apply this to morning sickness, eat more legumes/liver/cream/barley/oats/nuts and avoid sulfites (all over the place in processed foods) and nitrites. If you want to try taking molybdenum as a supplement, talk to your OB/GYN first because pregnancy is no time to experiment with large, chronic doses of anything.