The objective of this study was to investigate the effects of obstetric gel application on the length of the first stage of labour and perineal trauma in primiparous women. This randomised controlled trial included 110 primiparous women. Women were randomly assigned to the two groups: lubricant gel group and control group. In the intervention group, during cervical dilatation of 4 cm until complete cervical dilatation, 5 ml of water-soluble lubricant gel was used at each vaginal examination. In the control group, routine care was performed. Mean duration of the total length (p = .025), the first (p = .012), and second stage (p = .022) of labour was significantly shorter in the obstetric gel group than control group. Perineal health was significantly better in the gel-applied pregnant women (p < .001). Using obstetric gel at the beginning of the first stage could shorten the total length, the first and the second stage of labour and could protect perineal health.IMPACT STATEMENTWhat is already known on this subject? Prolonged labour and perineal injuries are a major problem in natural childbirth for primiparous mothers.What the results of this study add? The first (p = .012), and second stage (p = .022) of labour was significantly shorter in the obstetric gel group than in the control group. Perineal health was significantly better in gel-applied pregnant women (p < .001). Using obstetric gel at the beginning of the first stage could shorten the total length, the first and the second stage of labour and could protect against perineal injury.What the implications are of these findings for clinical practice and/or further research? Obstetrical gel lubricant usage in the first stage of labour during the active phase of nulliparous women could shorten the total length, the first and the second stage of labour and could protect perineal health.