Background:This study aims to compare the changes in the negative indices of mental health in pregnant women who participated in programs of either physical exercise classes or childbirth classes.Methods:The study was quasi-experimental in nature and run on 109 healthy primigravidae aged from 22 to 37, including 62 women participating in an exercise program (exercise group, E-group) for pregnant women and 47 women attending traditional childbirth classes (childbirth classes group, CC-group). The mental health assessment was performed using Goldberg’s General Health Questionnaire (GHQ-28).Results:The negative indices of mental health did not change over time. Lower levels of somatic symptoms and severe depression, as well as total score, were observed in the E-group (condition effect). Time × condition interactions, as well as analysis of change within the groups, indicated that in the CC-group all indices of disorders increased significantly, whereas in the E-group, only the increase of depression was significant.Conclusions:Regular physical exercises during pregnancy may constitute a factor in the prophylaxis of mental health disorders in pregnant women.