"Nausea in general is still very mysterious in the medical community — there are many pathways that lead to the nausea center in the brain, meaning that a person experiencing acute nausea can have many triggers," Kimber MacGibbon, RN, Director of Education and Research at the Hyperemesis Education and Research (HER) Foundation tells Refinery29. "That, along with the fact that it is unethical to do medical trials on pregnant women, has prevented us from reaching a full understanding of the condition."