Active labor usually occurs after the cervix dilates to ≥ 4 cm. Normally, cervical dilation and descent of the head into the pelvis proceed at a rate of at least 1 cm/hour and more quickly in multiparous women.
Etiology
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 (fetal dystocia).
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
Diagnosis of protracted labor is clinical.
The cause must be identified because it determines treatment.
Assessing fetal and pelvic dimensions and fetal position (part of a full obstetric examination) can sometimes determine whether the cause is fetopelvic disproportion. For example, fetal weight> 5000 g (> 4500 g in diabetic women) suggests fetopelvic disproportion.
Uterine dysfunction is diagnosed by evaluating the strength and frequency of contractions via palpation of the uterus or use of an intrauterine pressure catheter.
Diagnosis is often based on response to treatment.
Treatment
If the 1st or 2nd stage of labor proceeds too slowly and fetal weight is < 5000 g (< 4500 g in diabetic women), labor can be augmented with oxytocin, which is the treatment for hypotonic dysfunction. If normal progress is restored, labor can then proceed. If not, fetopelvic disproportion or intractable hypotonic dysfunction may be present, and cesarean delivery may be required.
If the 2nd 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.
The 2nd stage of labor is considered prolonged in the following cases:
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In nulliparous women: Lack of continuing progress for 4 hours with a regional anesthetic or 3 hours without a regional anesthetic
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In multiparous women: Lack of continuing progress for 3 hours with a regional anesthetic or 2 hours without a regional anesthetic (1)
Hypertonic uterine dysfunction is difficult to treat, but repositioning, short-acting tocolytics (eg, terbutaline 0.25 mg IV once), discontinuation of oxytocin if it is being used, and analgesics may help.
Treatment reference
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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
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Protracted labor may result from fetopelvic disproportion or from uterine contractions that are too weak or infrequent or, occasionally, too strong or close together.
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Assess fetal and pelvic dimensions and fetal position, and evaluate contractions by palpating the uterus or using an intrauterine pressure catheter.
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If the 1st or 2nd stage of labor proceeds too slowly and fetal weight is acceptably low, augment labor with oxytocin; if treatment is unsuccessful, the cause may be fetal disproportion or intractable hypotonic dysfunction, possibly requiring cesarean delivery.
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If the 2nd 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.
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For hypertonic uterine dysfunction, consider repositioning, short-acting tocolytics, discontinuation of oxytocin if it is being used, and analgesics.
