The assumption is frequently made that women with severe nausea and vomiting during pregnancy are transforming psychological distress into physical symptoms. Psychoanalytic theory supporting this assumption is reviewed, along with the few methodologically flawed empirical studies that have been conducted. Little support can be found for the hypothesis that nausea and vomiting during pregnancy is such a conversion disorder, but there are suggestions that psychological responses to the physiologic condition(s) underlying this problem may become entrenched, or conditioned. This possibility is supported by findings that psychological treatments, such as hypnosis, can be effective. This implies that psychological responses can interact with the physiology of nausea and vomiting during pregnancy to exacerbate the condition. As such, psychological treatments for the symptoms of this disorder need to be further explored.