Hyperemesis gravidarum in pregnancy is a serious condition that is often resistant to conservative treatments. Medical hypnosis is a well-documented alternative treatment. This article reviews the empirical studies of medical hypnosis for treating hyperemesis gravidarum, explains basic concepts, and details the treatment mechanisms. The importance of a thorough differential diagnosis and appropriate referrals is stressed. The article presents three case studies to illustrate the efficacy of this treatment approach. It is suggested that medical hypnosis should be considered as an adjunctive treatment option for those women with hyperemesis gravidarum. It is also stressed that medical hypnosis can be used to treat common morning sickness that is experienced by up to 80 percent of pregnant women. Its use could allow a more comfortable pregnancy and healthier fetal development, and could prevent cases that might otherwise proceed to full-blown hyperemesis gravidarum.