TABLE 1. Summary of the Articles Selected for Inclusion in the Review.

Authors—year of publication	Inclusion criteria	Stage of labor—information given	Breathing technique described	Stage of labor—use of breathing technique	When and how results were evaluated	Results
Almeida et al. (2005)	Primigravidae women with low-risk pregnancy and no associated pathology, in the latent stage of labor (≤ 4 cm), progression to normal delivery, no participation in antenatal preparation.	Information was provided during the latent stage and reinforcement given throughout labor.	Based on breathing techniques described by Read and Lamaze. Latent stage: Slow breathing with deep inhalation and exhalation. Active stage: Slow breathing with deep and prolonged inhalation and exhalation. Transition stage: Slow breathing, breathing deeply and holding the breath while pushing during contractions. Expulsion stage: Pressure breathing while bearing down.	Breathing techniques were used from the latent stage until expulsion stage.	The VAS scale was applied at the beginning of the latent, active and transition stages when the woman experienced pain. The STAI-T was applied during the latent stage of labor and the STAI-S during the active and transition stages, and immediately following delivery.	Women, who used breathing techniques, maintained a low level of anxiety through the latent, active and transition stages. No significant results in terms of pain during labor were reported. The duration of the latent stage was longer in the study group.
Lemos et al. (2011)	Primigravidae and multigravidae women 18–35 years old; with a low-risk pregnancy of 37–42 weeks and already admitted to the hospital.	Throughout the expulsion stage (between 10 cm of cervical dilatation and foetal expulsion).	Deep inhalation and apnea, Valsalva maneuver while bearing down.	Second stage of labor.	A chronometer was used to evaluate the duration of the expulsion stage. Pulse oximetry to measure oxygen saturation and a heart monitor to measure maternal heart rate were also used. In postpartum, the perineum was examined to evaluate the need of episiotomy and the degree of perineal trauma. Samples of umbilical cord blood, Apgar and newborn weight were evaluated.	Maternal outcomes were not associated with the duration of the Valsalva maneuver. A prolonged Valsalva maneuver was associated with reduced umbilical venous pH and venous base excess in the newborn infant.
Kamalifard et al. (2012)	Primigravidae women 20–35 years old and 36 weeks of gestational age.	Women received information at 36 weeks of pregnancy and at admission to the hospital.	Not specified.	Group I: Breathing techniques at 4 and 8 cm of dilatation. Group II: Breathing technique at 6 and 10 cm of dilatation. Group III: Massage at 4 and 8 cm of dilatation. Group IV: Massage at 6 and 10 cm of dilatation.	Thirty minutes after initiating the use of a technique, the VAS scale was used to evaluate pain. Blood pressure, pulse rate and body temperature were also evaluated. Partogram was used to evaluate the progression of labor and Apgar score to evaluate the vitality of the newborn.	There was a reduction in pain with breathing techniques at 4, 6, and 10 cm. of dilatation. However at 10 cm comparing the massage technique with breathing techniques, there was a significant reduction in pain.
Cicek et al. (2017)	Nulliparous women; 18–35 years old; 38–42 weeks of gestation without pregnancy complications, with a single healthy fetus in cephalic position; expected to have a spontaneous vaginal delivery, and in the early latent stage of labor (0–1 cm).	Information was provided at: The latent, active, transition and second stage of labor. Guidance and training were given for approximately 30 minutes.	First stage: Inhale slowly through the nose and exhale through the mouth. Second stage: Inhale through the nose to a count of 5 and exhale through the mouth in the same slow manner to a count of 5. Third stage: Breathe in and out rapidly through the mouth. The pattern includes the cleansing breath and the rhythmic hee-hee-hoo. Fourth stage: Breathe in and out through the mouth, with rapid and shallow blowing.	Throughout labor.	The STAI-S was used to asses’ anxiety. The duration of labor was evaluated by the researchers performed when the parturient women were at 0–1 cm, at 4 cm and at 8 cm of dilatation, respectively.	There was a reduction in anxiety at 8 cm of dilatation, and a reduction in the duration of the first stage of labor in the intervention group compared to the control group.
Boaviagem et al. (2017)	Pregnant women 12–40 years old, in active labor, with gestational age of 37–41 weeks.	Women received information during labor at 4 and 8 cm of dilatation.	At 4–6 cm of dilatation, women were instructed to breath slowly and deeply counting from 1 to 5 and to breathe out gradually counting from 5 to 1. At 7–10 cm of dilatation, women were instructed to slowly inhale through the nose and to breathe out through pursed lips.	Breathing techniques were performed for two consecutive hours after woman received the initial information	The STAI and VAS scales were applied 2 hours after the beginning of the intervention. The Modified Borg Scale was used to evaluate levels of maternal fatigue.	There was no significant difference between the intervention and control groups in relation to anxiety, pain, fatigue, or satisfaction.
Yuksel et al. (2017)	Nulliparous pregnant women at gestational age 37–42 weeks.	Women received information during the first stage of labor and received printed material for reinforcement of the information provided orally.	The women were instructed to breathe deeply and hold their breath for as long as possible while bearing down exhaling slowly.	Second stage of labor.	The VAS scale was used at the second stage of labor.	Pain was controlled and the duration of the second stage of labor was reduced (by ∼50 minutes).
Ahmadi et al. (2017)	Primiparous women, 18–35 years old with singleton pregnancy low-risk pregnancy at term, with cephalic presentation, candidate for vaginal delivery, who were at 3–5 cm of dilatation, normal and BMI (19.8–20.0).	Before the expulsion stage.	Women were instructed to take two deep breaths, then inhale and exhale through the mouth over 4–5 seconds while bearing down. In the control group, the Valsalva maneuver was used while bearing down.	Second stage of labor.	Pelvic floor was evaluated during labor and following delivery. Perineal trauma was assessed according to: Intact, posterior tear, anterior tear, episiotomy.	There was more probability of an intact perineum in women of the intervention group. The different forms of perineal tearing (1st-degree, 2nd-degree, 3rd-degree) was more frequent in the control group.

Note. BMI = body mass index; STAI = state-trait anxiety inventory; STAI-S = state anxiety scale; STAI-T = trait anxiety inventory; VAS = visual analogue scale.