A randomized clinical trial will be conducted to evaluate the effectiveness of using the Swiss Ball as a resource that reduces the length of labor time. The study will be conducted in the Low Risk Labor and Delivery sector of (Instituto Materno Infantil Professor Fernando Figueira) IMIP, which has a team of obstetric nurses, medical coordination and physical therapy support. The study population will be composed of low risk parturients admitted to the sector. Parturients who meet the inclusion criteria after signing the Informed Consent Form will be allocated into two groups: Group A (experimental) and Group B (control). Group A will be encouraged to use the Swiss Ball through pelvic movements, and Group B will go through the usual routine. Study results will be evaluated by assistants during labor and immediately after delivery.

Background: The Birth Ball, in childbirth care, has become a widely used resource in obstetrical centers, as it allows the adoption of vertical postures and exercises of pelvic mobility. It is an inexpensive and user-friendly feature that can facilitate pelvic exercise and thus contribute to positive maternal and neonatal outcomes.

Aim: To evaluate the effectiveness of the use of the Birth Ball compared to usual care in reducing the time of the first period of labor.

Methods: This is a randomized and pragmatic clinical trial that will be developed at the IMIP Childbirth Center in the state of Pernambuco. Pregnant women with normal risk, will be included in the first period of labor, with term gestation of the single and cephalic fetus, and pregnant women with a fetus dead, with a psychiatric disorder, using psychoactive drugs and in use of epidural analgesia or oxytocin prior to randomization. The sample size was calculated in 200 parturients, being randomly allocated 100 pregnant women for the experimental group and 100 for the control group, according to a list of random numbers specifically generated for this purpose. The duration of the first period of labor and, as secondary, pain, duration of the second period, birth routes, use of analgesia and oxytocin before randomization, fatigue, anxiety, maternal satisfaction, APGAR in the 5th neonatal resuscitation and hospitalization in a neonatal intensive care unit. The intervention group will use Birth Ball to perform active anteversion and pelvic retroversion exercises, lateralization and circumference according to the obstetric evaluation. The control group will receive the usual routine care of the service. Measurements will be made during and after fetal birth. The control group will receive the usual routine care of the service. Measurements will be made during and after fetal birth. To compare the continuous variables, the mean difference with the 95% Confidence Interval and Student's t-Test will be used. In order to compare the dichotomous variables, the Chi-square Test will be used. The Relative Risk will be calculated with the respective Confidence Interval of 95%. Data analysis will be performed using the Epi Info for Windows, version 3.5.4. The data will be presented in tables.

Ethical aspects: This study will comply with Resolution 466/12 of the National Health Council and will be submitted to the IMIP Research Ethics Committee, beginning only after its approval. All participants will only be included if they voluntarily agree to participate by signing the Free and Informed Consent Form. The research protocol will be registered in Clinical Trials.gov.

There are no conflicts of interest.

Inclusion Criteria:

• Pregnant woman in the first period of active labor;
• usual risk pregnancy;
• Single fetal pregnancy in cephalic presentation.

Exclusion Criteria:

• Pregnancy with dead fetus;
• Pregnant women with cesarean section indicated upon admission or until the time of approach;
• Pregnant women with limited mobility;
• Pregnant women with hip and pelvic fractures presenting difficulties in sitting position;
• Use of psychoactive drugs;
• Use of epidural analgesia or oxytocin before randomization.