Stress reduction care is important for pregnant women to decrease obstetric complications and children's health problems after birth. The aim of this study is to clarify the physical and psychologic effects of inhalation aromatherapy on pregnant women. Essential oils with high linalool and linalyl acetate content that may be used during pregnancy were selected and among these, and the one preferred by the participant was used. This was a prospective, randomized, controlled trial. This trial was performed at a gynecology outpatient department in a hospital in Kyoto, Japan. The study included pregnant women in week 28 of a single pregnancy with a normal course. Participants were randomly assigned into an aromatherapy group and a control group. They were seated in the resting, seated position for 10 minutes. During the latter 5 minutes of each 10-minute session, aromatherapy inhalation was performed for the aromatherapy group. Before and after the intervention, the Profile of Mood States (POMS) was measured. During the trial, the heart-rate fluctuations were measured for the autonomic nervous system regulation. A total of 13 pregnant women participated in the trial. Seven (7) participants were assigned to the aromatherapy group and 6 participants to the control group. The results of the POMS were such that based on an intragroup comparison, significant differences were observed in the Tension-Anxiety score (p<0.05) and the Anger-Hostility score (p<0.05), and the respective improvements observed were due to aromatherapy. The results of the autonomic nervous system regulation were such that based on an intragroup comparison within the aromatherapy group, the parasympathetic nerve activity increased significantly (p<0.05). Aromatherapy inhalation using essential oils containing linalyl acetate and linalool was found to be effective for the POMS and parasympathetic nerve activity, based on an intragroup comparison. However, based on a comparison between the groups, no substantial difference was observed; hence, further study is necessary in the future.