Progresión Laboral Normal y Anormal - UpToDate

10/1/2018

Progresión laboral normal y anormal - UpToDate

Autores: Robert M Ehsanipoor, MD, Andrew J Satin, MD, FACOG Editor de sección: Vincenzo Berghella, MD Editor Adjunto: Vanessa A Barss, MD, FACOG Divulgaciones del colaborador

Todos los temas se actualizan a medida que hay nuevas pruebas disponibles y nuestro proceso de revisión por pares está completo. Revisión bibliográfica actual hasta: dic. 2017. | Última actualización de este tema: 13 de octubre de 2017. INTRODUCCIÓN - Durante el trabajo de parto normal, las contracciones uterinas regulares y dolorosas causan dilatación progresiva y borramiento del cuello uterino, acompañado de descenso y eventual expulsión del feto. "Trabajo de parto anormal", "distocia" y "falta de progreso" son términos tradicionales pero imprecisos que se han utilizado para describir un patrón de trabajo que se desvía del observado en la mayoría de las mujeres que tienen un parto vaginal espontáneo. Estas anomalías laborales se describen mejor como trastornos de la protracción (es decir, más lentos que el progreso normal) o trastornos de la detención (es decir, el cese completo del progreso). - Por convención, una fase activa anormalmente larga generalmente se describe como prolongada, mientras que una fase latente anormalmente larga o una segunda etapa generalmente se describe como prolongada. Este tema describirá el progreso laboral normal y discutirá el diagnóstico y el tratamiento de los trastornos de detención y arresto. El manejo del trabajo de parto y parto normal se revisa por separado. (Consulte "Gestión del trabajo de parto y parto normales" ). PROGRESIÓN NORMAL DEL PARTO - Aunque determinar si el trabajo de parto progresa normalmente es un componente clave del cuidado intraparto, determinar el inicio del parto, medir su progreso y evaluar los factores (poder, pasajeros, pelvis) que afectan su curso son una ciencia inexacta. Etapas y fases : la interpretación del progreso laboral depende de la etapa y la fase. Las tres etapas y sus fases son: ● Primera etapa : tiempo desde el inicio del parto hasta completar la dilatación cervical. Clínicamente, a las mujeres simplemente se les pregunta el momento en que creen que comenzó el trabajo de parto (es decir, cuando las contracciones comenzaron a ocurrir regularmente cada 3 a 5 minutos durante más de una hora) para documentar el comienzo del trabajo de parto. El momento en que la dilatación completa se identifica por primera vez en el examen físico documenta el final de la primera etapa. Los tiempos precisos tanto del comienzo del trabajo de parto como de la dilatación completa son imposibles de determinar ya que el útero normal se contrae de forma intermitente e irregular durante la gestación, las contracciones iniciales iniciales al inicio del parto son leves e infrecuentes, los cambios cervicales iniciales son sutiles y físicos. el examen para documentar el cambio cervical se realiza de forma intermitente. La primera etapa consiste en una fase latente y una fase activa . La fase latente se caracteriza por un cambio gradual en el cuello uterino y la fase activa se caracteriza por un cambio cervical rápido. La curva de trabajo de multiparas puede mostrar un punto de inflexión entre las fases latente y activa; este punto ocurre a unos 5 cm de dilatación [ 1 ]. En nulíparas, el punto de inflexión a menudo no está claro y, si está presente, se produce en una dilatación cervical más avanzada, por lo general a aproximadamente 6 cm o más. En cualquier caso, este punto de inflexión es un hallazgo retrospectivo. ● Segunda etapa : tiempo desde la dilatación cervical completa hasta la expulsión fetal.

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Progresión laboral normal y anormal - UpToDate

When pushing is delayed, some clinicians divide the second stage into a passive phase (from complete cervical dilation to onset of active maternal expulsive efforts) and an active phase (from beginning of active maternal expulsive efforts to expulsion of the fetus) [2]. ● Third stage – Time between fetal expulsion and placental expulsion. Criteria for normal progress — Emanuel Friedman established criteria for the normal progress of labor in the 1950s, and these criteria were used for assessment and management of labor for decades. However, data derived from women in labor in the 21st century suggest that changes in obstetric and anesthesia practices and in women themselves in recent decades have resulted in changes in the average progress of labor. Therefore, criteria for normal labor progress have been revised, although this remains controversial. Friedman (historic) criteria — Emanuel Friedman conducted his now classic studies defining the spectrum of normal labor by evaluating the course of labor of 500 primigravidas admitted to the Sloane Hospital for Women in New York in the mid-1950s [3-5]. The norms established by his data, depicted as the "Friedman curve" (figure 1), were widely accepted as the standard for assessment of normal labor progression for decades. Based on these data, the transition from the latent phase to active phase appeared to occur at 3 to 4 cm cervical dilation, and the statistical minimum rate (5th centile) of normal cervical dilation during the active phase was 1.2 cm/hour for nulliparous women and 1.5 cm/hour for multiparous women. A prolonged second stage for nulliparas and multiparas was defined as three hours and one hour, respectively. Contemporary criteria — The applicability of the Friedman curve and its established norms to contemporary obstetric practice was challenged in the 21st century. Several studies evaluated labor curves in thousands of contemporary women to establish contemporary criteria for normal labor progression [6-8]. These criteria are different from, and generally slower than, those cited by Friedman. This change has been attributed to changes in patient characteristics (eg, higher mean body mass index), anesthesia practices (more use of neuraxial anesthesia), and obstetric practices over the past half-century. In addition, a limitation of Friedman's findings is that his data were based on labors in only 500 women who were managed at a single institution. However, revision of the classic labor curve as described by Friedman has not been accepted universally. For example, Friedman and Cohen argue that the shape of the curve may have been influenced by selection biases and confounders [9,10]. The most appropriate statistical methods remain debated. First stage — Zhang and colleagues obtained data on normal labor patterns by evaluating contemporary data from the Consortium on Safe Labor, which included information on 62,415 singleton pregnancies with spontaneous onset of labor, cephalic vaginal delivery (≥88 percent spontaneous), and normal neonatal outcome [6]. The data were collected retrospectively from the electronic medical records at 19 medical centers in the United States. These data have been used to define normal labor progress, as shown in the table (table 1). The shape of the normal labor curve generated from Zhang's data (figure 2) is different from the Friedman curve (figure 1). The Friedman curve depicts a relatively slow rate of cervical dilation until approximately 4 cm (ie, latent phase), which is followed by an abrupt acceleration in the rate of dilation (ie, active phase) until entering a deceleration phase at approximately 9 cm. Zhang's labor curves also demonstrate an increase in the rate of cervical dilation as labor progresses, but the increase is more gradual than that described by Friedman: Over 50 percent of patients did not dilate >1 cm/hour until reaching 5 to 6 cm dilation, and a deceleration phase at the end of the first stage of labor was not observed. Labor curves constructed from other contemporary data sets also generally differ from Friedman's curve [7,11]. Specifically, there is no abrupt change in the rate of cervical dilation indicating a https://www.uptodate.com/contents/normal-and-abnormal-labor-progression?search=labor%20de%20parto&source=search_result&selectedTitle…

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clear transition from latent to active phase and there is no deceleration phase at the end of the first stage of labor. While the presence or absence of a deceleration phase at the end of the 1st stage of labor is not of major clinical significance, defining the transition from latent to active phase (ie, transition from slower to more rapid cervical dilation) is clinically important for diagnosing labor abnormalities. Contemporary data suggest that the normal rate of cervical change between 3 and 6 cm dilation is much slower than described by Friedman, who reported minimum dilation should be at least 1 cm/hour [7,12]. Many contemporary women who go on to deliver vaginally have rates of cervical dilation 200 MVU if an internal pressure catheter is in place), or six hours without adequate uterine contractions and no cervical change in the active phase of labor, we proceed with cesarean delivery. If labor is progressing, either slowly or normally, we continue oxytocin at the dosage required to maintain an adequate uterine contraction pattern. Dosing regimen — Numerous oxytocin dosing protocols that vary in initial dose, incremental dose increase, and time interval between dose increases have been studied (table 3). (See "Induction of labor with oxytocin", section on 'Dose titration and maintenance'.) The decision to use a high- versus a low-dose oxytocin regimen poses a risk-benefit dilemma: Higherdose regimens are associated with shorter labor and fewer cesareans but more tachysystole (>5 contractions in 10 minutes, averaged over a 30-minute window). The value placed on each of these outcomes and the ability to respond to tachysystole may vary among labor and delivery units. Therefore, either a high- or low-dose oxytocin regimen is acceptable and should depend on local factors. We use a high-dose regimen and do not alter our management based on parity [42,63,64], with one important exception: We do not use a high-dose regimen in women who have had a previous cesarean delivery because of risk of rupture [63]. Low-dose regimens were developed, in part, to avoid uterine tachysystole and are based upon the observation that it takes 40 to 60 minutes to reach steady-state oxytocin levels in maternal serum [65]. A 2010 systematic review of randomized trials of high- versus low-dose oxytocin for augmentation of women in spontaneous labor (10 trials, n = 5423 women) found that high-dose oxytocin [66]: ● Increased the frequency of tachysystole (relative risk [RR] 1.91, 95% CI 1.49-2.45) ● Decreased the cesarean delivery rate (RR 0.85, 95% CI 0.75-0.97) and increased the rate of spontaneous vaginal delivery (RR 1.07, 95% CI 1.02-1.12) ● Decreased the total duration of labor (mean difference -1.54 hours, 95% CI -2.44 to -0.64 hours) ● Resulted in similar maternal and neonatal morbidities A 2013 systematic review had fewer trials because it excluded those involving augmentation as part of an active management of labor protocol, but came to similar conclusions [67]. Ineffective and less well studied approaches ● Misoprostol – Oxytocin with or without amniotomy is the best approach for treatment of a protraction disorder, based on extensive experience and data attesting to safety and efficacy. The body of evidence does not support using any alternative pharmacologic approach. Misoprostol is typically used for cervical ripening and labor induction; there are limited data on its safety and efficacy for treatment of protraction disorders [68,69]. However, low-dose titrated misoprostol may be a reasonable alternative in low-resource settings where safe oxytocin infusion is not feasible. ● Ambulation may improve the comfort of the parturient and is not harmful, but there is no convincing evidence that this intervention prevents or treats protraction or arrest disorders [70]. Active phase arrest — Women with labor arrest in the active phase of the first stage are managed by cesarean delivery. The key issue is using appropriate criteria for diagnosing labor arrest. Some https://www.uptodate.com/contents/normal-and-abnormal-labor-progression?search=labor%20de%20parto&source=search_result&selectedTitle…

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unnecessary cesareans will be performed in arrest is diagnosed too soon, and maternal complications (eg, uterine rupture) are likely to increase if arrest is diagnosed too late. We use the criteria described above, proposed by a workshop convened by the NICHD, SMFM, and ACOG and based on contemporary data criteria. (See 'Arrest' above.) These criteria were based on the following studies. These studies showed that oxytocin augmentation for at least four hours, rather than the historical standard of two hours, before diagnosing arrest is safe for mother and fetus and increases the chances of achieving a vaginal delivery. They also show that vaginal delivery is often possible despite levels of uterine activity and rates of cervical dilation below the range historically considered necessary for success. ● A prospective study including 542 women in spontaneous labor at term with active phase labor arrest (defined as cervix ≥4 cm dilated and ≤1 cm of cervical progress in four hours) evaluated a protocol whereby oxytocin augmentation was initiated and cesarean delivery was not performed for labor arrest until (1) the woman experienced at least four hours uterine contractions >200 MVUs or (2) the woman experienced a minimum of six hours of oxytocin augmentation if this contraction pattern could not be achieved [42]. Only 12 percent of women did not achieve the target 200 MVUs. The authors found that 91 percent of multiparas and 74 percent of nulliparas who had not progressed (≤1 cm additional dilation) by the traditional two hours of oxytocin administration and thus would have undergone cesarean delivery at that time went on to achieve a vaginal delivery. Indeed, waiting at least four hours before performing a cesarean for labor arrest allowed 88 percent of multiparas and 56 percent of nulliparas to achieve a vaginal delivery. ● The same investigators subsequently used a standardized protocol to manage 501 consecutive, term, spontaneously laboring women with slow labor progress [43]. The protocol involved administration of oxytocin to achieve at least 200 MVUs for four hours before considering cesarean delivery. In this study, 80 percent of nulliparous women and 95 percent of multiparous women had a vaginal delivery, whether or not they were able to achieve and/or maintain the MVU goal. Mean (5th percentile) rates of cervical dilation in nulliparas and multiparas were 1.4 cm/hour (0.5) and 1.8 cm/hour (0.5), respectively. Prevention of first stage labor abnormalities — There is no strong evidence that any intervention will prevent first stage protraction and arrest disorders. Amniotomy is the most common intervention that has been proposed for shortening the duration of labor. Routine amniotomy alone versus intention to preserve the membranes (no amniotomy) did not clearly shorten the first or second stage in a meta-analysis of randomized trials [71]. However, in another metaanalysis, the combination of early amniotomy and early oxytocin administration versus routine care for women in spontaneous labor shortened the first stage (mean difference -1.57 hours, 95% CI -2.15 to -1.00), and possibly resulted in a small decrease in cesarean delivery (RR 0.87, 95% CI 0.77-0.99) [58]. The potential small benefits of the combined intervention are not sufficiently compelling to warrant a recommendation for a change in routine management of spontaneous labor. (See "Management of normal labor and delivery", section on 'Amniotomy'.) Avoiding or delaying neuraxial anesthesia to potentially reduce the risk of labor abnormalities is not recommended. ACOG has stated that the decision to place a neuraxial anesthetic should depend upon the patient's wishes with consideration of factors, such as parity, also taken into account [72]. In particular, concern about future labor progress should not be a reason to require a woman to reach an arbitrary cervical dilation, such as 4 to 5 cm, before fulfilling her request to receive neuraxial anesthesia. PROLONGED SECOND STAGE

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Diagnosis — The appropriate duration and maximum length of time allowed for the second stage of labor is not clearly defined. Parity, regional anesthesia, and delayed pushing in addition to other clinical considerations all significantly impact the length of the second stage. We follow the 2014 Obstetric Care Consensus statement of recommendations for safe prevention of primary cesarean delivery by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine [73]. These recommendations are used as a pragmatic approach for diagnosis of a prolonged second stage and are supported by the data from Zhang et al (table 1), which we believe is the best guide for establishing the normal duration for the second stage of labor (median and 95th centile). The following is a summary of the statement/recommendations [73]: ● For nulliparous women, allow three hours of pushing, and for multiparous women, allow two hours of pushing prior to diagnosing arrest of labor, when maternal and fetal conditions permit ● Longer durations may be appropriate on an individual basis (eg, epidural anesthesia, fetal malposition) as long as progress is being documented ● A specific absolute maximum length of time that should be allowed in the second stage of labor has not been identified Based on these recommendation and those of a 2012 workshop (National Institute of Child Health and Human Development workshop Preventing the First Cesarean Delivery) [56], many obstetric providers allow an extra hour of pushing for women with an epidural, and good outcomes have been reported [74]. Of note, this statement does not provide specific criteria for the upper limit of the second stage; it merely states that arrest should not be diagnosed before passage of a specific minimum period of time. It should also be noted that the use of these criteria has been challenged by some experts, who believe that the safety of extending the second stage to these lengths, particularly in nulliparous women with an epidural, has not been established [9,75]. Assessing progressive, but small, degrees of descent and rotation by physical examination is challenging. Additional physical findings can support the diagnosis of arrest due to cephalopelvic disproportion. The soft bones and open sutures of the fetal skull (figure 6) allow it to change in shape (ie, molding) and thus adapt to the maternal pelvis during descent. Some overlap of the parietal and occipital bones at the lambdoid sutures and overlap of the parietal and frontal bones at the coronal sutures is common in normal labor [47]. However, lack of descent with severe molding, especially overlap of the parietal bones at the sagittal suture, is suggestive of cephalopelvic disproportion. Likewise, lack of descent with malposition or malpresentation is suggestive of cephalopelvic disproportion. Management Candidates for oxytocin augmentation — After 60 to 90 minutes of pushing, we begin oxytocin augmentation if descent is minimal (ie,