Background There is limited information on the changes in uncomplicated pregnancies. Therefore, in the present study, the changes of depression and anxiety changes in uncomplicated pregnancies during the prenatal period was evaluated.Method This longitudinal study was performed on 256 pregnant women at the beginning of the first trimester of pregnancy. Inclusion criteria included the absence of pre-pregnancy depression and anxiety and poor pregnancy history. Exclusion criteria were the incidence of pregnancy complications. The level of their depression and anxiety at the time of entering the study were completed by self-report using the DASS questionnaire at 9–10, 11–12, 24–25, and 33–35 weeks of pregnancy.Results The results of the study indicated the effect of time on the level of perinatal depression and anxiety (p < 0.001). These findings showed that the level of depression increased significantly from 9 to 24 weeks of pregnancy and decreased in the 32–34 weeks, but did not reach the level of depression at 9 weeks of pregnancy. Also, the anxiety level increased significantly from the onset of pregnancy to the 24 weeks gestation but did not change during the second and third trimesters. The findings of the study showed that depression and anxiety levels in each of the pregnancy termites were related to its level in the previous trimesters.Conclusion The results of the study showed that the level of depression and anxiety of women in uncomplicated pregnancies also increases. Therefore, psychological health screenings in the second trimester of pregnancy should be performed in these women.