Participants, researchers, and center

All participants were recruited from among the parturients admitted to the Reference Centre of Women's Health of Ribeirão Preto-MATER, São Paulo, Brazil, from May 2012 to July 2015. The inclusion criteria were low-risk primigravida at > 37 weeks of gestation with a single fetus in the cephalic position, spontaneous onset of labor, cervical dilation of 4 to 5 cm and ≥2 uterine contractions, intact ovular membranes, and the ability to read the consent form and understand the study. The exclusion criteria were the use of analgesic medications or other drugs that interfere with uterine contraction from hospital admission to randomization, cognitive or psychiatric problems, or other risk factors (gestational hypertension or gestational diabetes mellitus). The reasons to stop the intervention protocol were as follows: the participant desired to stop or had an intolerance to the NPR application because of pain, fetal compromise; cesarean delivery performed before the end of the research protocol, and an inability to obtain relevant data from maternal and neonatal medical records. The participants were free to withdraw from the study at any stage.

Although the primary researcher was a physiotherapist with 4 years of clinical experience, there was a standardization of the methods to evaluate labor pain to minimize the researcher's interference. The therapists assumed the same role (ie, the primary researcher performed randomization and application of the protocol or routine care, whereas the blinded researcher measured the outcomes). The baby's heart rate was evaluated every 30 minutes by the doctor as a way of identifying any fetal distress.