Background Performing exercise with medium intensity has positive effects on the maternal health. The aim of this study was to investigate the effectiveness of Pilates exercise program during pregnancy on childbirth outcomes: Methods This clinical trial study was performed on 110 primiparous women who were randomly divided into two groups of intervention (n = 55) and control (n = 55). The intervention group performed Pilates exercises from 26 to 28 weeks of gestation for 8 weeks while the control group did not do any exercise. Data collection tools included Visual Analog Scale (VAS), Mackey Childbirth Satisfaction Rating Scale, and a checklist including demographic and obstetrics information. Results The results of the study showed that Pilates exercise during pregnancy significantly reduces the labor pain intensity, length of the active phase and second stage of labor and increases maternal satisfaction of the labor process (p < 0.05). Based on the Kaplan Meyer analysis, the mean whole length of labor was shorter in Pilates exercise group than in the control group (P = .004). There was no statistically significant difference between the two groups in terms of Episiotomy, type of delivery, first and fifth Apgar score of neonates (p > 0.05). Conclusion According to the results of this study, Pilates exercise during pregnancy improved the labor process and increased maternal satisfaction of chidbirthprocess, without causing complications for the mother and baby. However, studies with larger sample sizes are recommended to prove the efficacy and safty of this practiceduring labor. Trial registration IRCT registration number:IRCT20200126046266N1. Registration date: 2020-05-02 (retrospectively registered).