There seems to be strong evidence to support the hypothesis that eating ginger helps reduce nausea e.g. during pregnancy (e.g. Vutyavanich et al.). It seems that gingerol is the active ingredient in preventing nausea (cf. Qian et al.). Wikipedia writes: "Cooking ginger transforms gingerol into zingerone...". Presumably, zingerone does not affect nausea.
Question: Does cooking ginger reduce its anti-nausea effect?
A Google search will reveal numerous suggestions for giving ginger tea to pregnant women to help with morning sickness. But boiling the ginger could conceivably defeat the purpose of taking the ginger in the first place (and any effects are primarily due to the placebo).
There's an article (Basirat et al.) which describes an experiment in which biscuits with ginger were given to patients (instead of ginger tablets), although their results alone have not convinced me one way or the other. The authors conclude that their results indicate an anti-nausea effect, but some of their tests do not match that conclusion (i.e. a placebo was comparably effective). Also, the group given the ginger biscuits started off with worse conditions on average.