In the first stage of labor, cervical dilation may be gradual during the latent phase but then accelerated during the active phase, starting at ≥ 4 to 6 cm (1).
General reference
1. Zhang J, Landy HJ, Branch DW, et al: Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116 (6):1281–1287, 2010. doi: 10.1097/AOG.0b013e3181fdef6e
Etiology of Protracted or Arrested Labor
Protracted labor may result from fetopelvic disproportion (the fetus cannot fit through the maternal pelvis), which can occur because the maternal pelvis is abnormally small or because the fetus is abnormally large or abnormally positioned (abnormal presentation, lie, or position).
Another cause of protracted labor is uterine contractions that are too weak or infrequent (hypotonic uterine dysfunction) or, occasionally, too strong or close together (hypertonic uterine dysfunction).
Diagnosis of Protracted or Arrested Labor
Cervical examination
Assessment of uterine contractions
Diagnosis of protracted labor is clinical.
If a cause is identified, it may contribute to the decision to continue labor or to proceed with an operative vaginal delivery or cesarean delivery.
Estimating fetal weight through physical examination or ultrasonography when the patient is in the first stage of labor is helpful to determine if fetal macrosomia (fetal weight > 5000 g [> 4500 g in diabetic women]) is present. In addition to being a cause of protracted labor, fetal macrosomia is also a risk factor for shoulder dystocia and severe perineal laceration, and appropriate preparations should be made.
Uterine dysfunction is diagnosed by evaluating the strength and frequency of contractions via palpation of the uterus or use of an intrauterine pressure catheter.
Determining standard criteria for labor protraction or arrest for each stage of labor has been the subject of controversy, and there are no standard definitions. Commonly used criteria for protraction or arrest for each stage or phase include:
First stage, latent phase: Protraction is > 20 hours in nulliparous patients or > 14 hours in multiparous patients (some studies have reported longer durations) (1).
First stage, active phase: Protraction is, after 6 cm dilation is reached, cervix dilation < 1.2 cm/hour in nulliparous patients or < 1.5 cm/hour in multiparous patients. Active-phase arrest is typically defined as no change in cervical dilation for 2 to 4 hours.
Second stage: Arrest is at least 3 hours of pushing in nulliparous women or at least 2 hours in multiparous women (add 1 hour to these definitions when epidural anesthesia is used) (2).
Third stage: Normal duration is ≤ 30 minutes.
Diagnosis references
1. Tilden EL, Phillippi JC, Ahlberg M, et al: Describing latent phase duration and associated characteristics among 1281 low-risk women in spontaneous labor. Birth 46(4):592-601, 2019. doi:10.1111/birt.12428
2. Obstetric care consensus no. 1: safe prevention of the primary cesarean delivery. Obstet Gynecol. 123(3):693-711, 2014. doi:10.1097/01.AOG.0000444441.04111.1d
Treatment of Protracted or Arrested Labor
Sometimes operative delivery if the second stage of labor is prolonged
Cesarean delivery
If the first or second stage of labor is protracted or arrested and fetal weight is < 5000 g (<cesarean delivery may be required.
If the second stage of labor is prolonged, forceps or vacuum extraction may be appropriate after evaluation of fetal size, presentation, and station (2 cm below the maternal ischial spines [+2] or lower) and evaluation of the maternal pelvis.
Treatment reference
1. Spong CY, Berghella V, Wenstrom KD, et al: Preventing the first cesarean delivery: Summary of a Joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists Workshop. Obstet Gynecol 120 (5):1181–1193, 2012. doi: http://10.1097/AOG.0b013e3182704880
Key Points
Protracted labor may result from fetopelvic disproportion or from uterine contractions that are too weak or infrequent or, occasionally, too strong or close together.
Assess fetal and pelvic dimensions and fetal position, and evaluate contractions by palpating the uterus or using an intrauterine pressure catheter.
If the second stage of labor is prolonged, consider forceps or vacuum extraction if appropriate after evaluating the fetus's size, position, and station and the maternal pelvis.
