Episiotomy was not performed for any participants in either group, and there were no third- or fourth-degree tears. The frequency distribution of perineal tears based on their degree showed no significant difference between the two groups. In the present study, none of the participants in either group received oxytocin. The use of oxytocin is a risk factor for an increase in perineal damage (
24). It is possible that the absence of oxytocin administration contributed to the absence of severe perineal damage in the present study. Previous studies have demonstrated that spontaneous pushing and allowing mothers to choose their preferred labor positions can reduce the risk of perineal damage (
25,
26). The results of the present study were consistent with those of a semi-experimental study, which found no significant difference in the application of episiotomy or the frequency of first- and second-degree perineal tears between upright positions (where mothers were in an upright position during the first stage of labor and in a hands and knees position during the second stage) and the supine position. Furthermore, no cases of third- or fourth-degree tears were observed (
15). Also, in another study, no significant relationship was observed between positions with a flexible sacrum and the occurrence of tears requiring repair or anal/rectum sphincter tear. In positions with a flexible sacrum, the need for episiotomy was lower compared to other groups (P < 0.01) (
27). The results of the present study were consistent with the mentioned study. On the contrary, in a different study, the frequency of no perineal tear and first-degree tear was higher in the hands and knees group compared to the supine group (P < 0.001). However, the frequency of second-degree tears was significantly lower in the supine group compared to the hands and knees group (P < 0.001). The results of the present study were inconsistent with the mentioned study. The researchers of the mentioned study claimed that the improvement of perineal blood supply was the reason for the decreased occurrence of second-degree tears in the hands and knees group (
4). In the mentioned study, unlike the present study, different midwives/obstetricians were involved in the deliveries, and the varying skill levels of these practitioners could have influenced the results. Additionally, in the mentioned study, the hands and knees position involved raising the bed’s head by 30 to 60 degrees. In contrast, in the present study, the mothers maintained a completely horizontal position with their shoulders and hips at the same level during hands and knees positions. The results of the present study were different from those of a semi-experimental study where the frequency of perineal damage was lower in positions with a flexible sacrum compared to positions with a non-flexible sacrum (P < 0.05) (
16). The results of the present study contradicted the mentioned study. In both the control and intervention groups, mothers were assigned from the beginning of the active phase of labor. Upright positions have been shown to improve blood supply to the pelvis (
1). Upright positions such as sitting, squatting, and upright kneeling can shorten the duration of the second stage of labor, resulting in a faster delivery of the fetus through the birth canal. This reduced duration may increase the risk of a perineal tear due to less time for tissue stretching and traction. Conversely, lying on the side and hands and knees positions, which do not expedite the second stage of labor, allow mothers to freely move their pelvis, minimize external pressure on the perineum, provide better access for the labor assistant to support the perineum, and reduce the pressure on the perineum, thereby decreasing the risk of damage (
23).