Paul Lyons1
(1)
Department of Family Medicine, University of California, Riverside, Riverside, CA, USA
Key Points
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Background
Most pregnancies will proceed with a minimum of abnormality and delivery will occur without significant complications. All deliveries have the potential for complications; providers should be aware of and prepared for the potential complications associated with delivery of the infant.
Complications of Labor
Labor is defined as uterine contractions resulting in progressive cervical dilation, effacement, and eventual delivery of the infant. The normal course of labor is reviewed in Chap. 19. In general the progression of labor depends on three identifiable factors: adequate uterine contraction (both frequency and force), fetal size and position, and adequate pelvic anatomy to allow descent. Routine labor management includes sequential assessment of labor progress via manual examination of the cervix and presenting fetal body part. Although labor is predictable and progressive in most patients, under some circumstances the normal progression is disturbed. These may include a delay in the transition from latent- to active-phase labor, failure of cervical dilation to occur, and occurrence of dilation without fetal descent.
Prolonged Latent-Phase Labor
Latent-phase or early labor is the period marked by contractions and initial cervical dilation. The contractions are generally frequent and less strong than those of active labor and the progress of cervical dilation may be variable. Although average latent-phase labor lasts between 5 and 8 h, there is considerable variability. Often, the management of latent-phase labor occurs outside the medical facility. Ideally, patients without obstetrical complications or medical risk factors would arrive at the hospital in active labor, having self-managed the latent phase of labor.
Under some circumstances, however, patients will present for management while in latent-phase labor. When the latent phase of labor has continued significantly beyond the expected duration (>20 h in nulliparous patients and >14 h in multiparous patients), management decisions must be made. Most patients with prolonged latent-phase labor will progress to active labor and subsequent vaginal delivery.
History
Management begins with a review of the patient’s history. Review of the gestational age, prenatal course, and prior obstetrical history, if any, should be performed. Although most instances of prolonged latent-phase labor are idiopathic, use of sedation and alcohol and prior episodes of prolonged labor may all be associated with a prolonged latent phase.
Physical Examination
Assessment of cervical status is the key physical finding. Cervical dilation, effacement, and fetal descent should all be noted. Rupture of membranes should also be noted, as management will vary if membranes are ruptured. Documentation at regular intervals will assist in determining the rate of labor progression and the degree to which the current pregnancy deviates from the norm. As feto–pelvic disproportion may contribute to a prolonged latent-phase assessment of fetal size, presentation and pelvic adequacy should be noted.
Laboratory/Diagnostic Studies
Generally, diagnostic studies are of limited value in the management of prolonged latent-phase labor. Obstetrical ultrasound may assist in assessment of fetal size and examination of pooled vaginal fluids, if any, may contribute to assessment of possible rupture of membranes. Fetal heart tones should be monitored intermittently to assess fetal well-being.
Management
Most patients with prolonged latent-phase labor require no specific intervention. Of patients with latent-phase labor, 10–15 % will show little if any cervical change. These patients have not yet started true labor and may be sent home to rest or walk, with precautions concerning when to return. Rest and hydration will result in active labor in the majority of patients (80–85 %) who are kept in the hospital. A small percentage (5–10 %) will demonstrate active uterine contractions but insufficient cervical dilation. These patients may benefit from the use of oxytocin to augment labor. Patients with ruptured membranes should be admitted and monitored for signs or symptoms of infection. Details concerning the management of such patients can be found in Chap. 8.
Failure to Dilate/Efface
With the onset of active labor, most patients can be expected to follow a predictable pattern of cervical dilation and effacement. As noted in Chap. 19, expected dilation is approximately 1 cm per hour for primigravid patients and 1.2–1.5 cm per hour for multiparous patients. Total duration of active first-stage labor is approximately 10 h (6–18 h) for primigravid and 5 h (2–10) for multiparous patients. Documented failure to dilate at the expected rate despite the presence of organized uterine contractions is a second complication of labor.
The underlying etiology for failed cervical dilation is not well understood. Broadly understood, the problem may be with the fetus (size, presentation), with the birth canal (feto–pelvic disproportion), or with the uterine forces necessary to complete expulsion of the fetus. Evaluation of failure to dilate requires assessment of each of these components.
History
The history may contribute to assessment of risk factors associated with either the fetus or the birth canal. The patient’s prenatal course should be reviewed, with a particular emphasis on malpresentation and risk factors for macrosomia such as gestational diabetes. Past obstetrical history should also be reviewed for prior failure to dilate, past history of gestational diabetes, or prior macrosomic infants. Feto–pelvic disproportion is largely a diagnosis of exclusion; however, those patients with bony abnormalities of the birth canal can be expected to have recurrent difficulties.
Physical Examination
Physical examination contributes significantly to the diagnosis and management of delayed cervical dilation. Serial cervical examination to assess dilation, effacement, and station should be performed and the results plotted on a normal labor curve. Identification of abnormal presentation may be apparent on physical examination. Abnormal presentations such as occiput posterior, brow, or face presentation occur in approximately 5 % of all deliveries and should generally be apparent on examination. Breech presentation with abnormal presenting fetal body parts may also be determined on pelvic examination. An assessment of fetal size should be performed, as ultrasound assessment of fetal size at term may be inaccurate. Although the reliability of manual assessment of pelvic adequacy has been questioned, a brief evaluation of the birth canal should also be performed as a part of the pelvic examination.
Critical to the assessment and management of prolonged dilation is an assessment of the adequacy of uterine contractions. Although external monitors may be useful for determining the frequency of uterine contractions, determination of the strength of those contractions requires the placement of an intrauterine pressure catheter (IUPC).
Laboratory/Diagnostic Studies
In general, laboratory and diagnostic studies are limited in the management of delayed cervical dilation. An obstetrical ultrasound may assist in the assessment of fetal size or presentation.
Management
Management of delayed cervical dilation requires assessment of which, if any, identifiable factors are contributing to the delay. The management of malpresentation is covered later. The indications for operative delivery are reviewed in Chap. 21.
In the absence of clearly contributory factors such as malpresentation or macrosomia, adequacy of uterine contractions should be assessed. Placement of an IUPC allows for calculation of the adequacy of uterine contractile activity. The most common and simplest measure of uterine activity is the Montevideo unit, measured as the increase in intrauterine pressure with contractions (maximum pressure–baseline pressure) over a 10-min period. The Montevideo units for each contraction are calculated and all contractions in a 10-min period are added together. A total of 200 Montevideo units are considered evidence of adequate uterine contractile activity.
For patients without adequate uterine contractile activity, oxytocin augmentation should be administered until adequate contractions are established. Cervical dilation should be periodically documented thereafter. Failure to dilate may be diagnosed with 2 h of adequate uterine contractions and no cervical change. If cervical dilation is occurring, management depends on the status of the infant. Slow but steady cervical dilation (with or without oxytocin augmentation) should be allowed to progress unless evidence of fetal stress is noted.
Patients for whom inadequate uterine contractile activity is the only apparent source of incomplete cervical dilation will generally have an excellent outcome, with two-thirds eventually delivering vaginally.
Failure to Descend
Despite full cervical dilation, the fetus may fail to descend through the birth canal. Although inadequate uterine contractile activity contributes to many of these cases, feto–pelvic disproportion makes up roughly half them. Evaluation is similar to that for failure to dilate. Particular attention should be paid to clinical evidence of pelvic adequacy, fetal size, and malpresentation. If clinical evidence suggests feto–pelvic disproportion, consideration should be given to cesarean section delivery. In the absence of clinical evidence of feto–pelvic disproportion, assessment of uterine activity adequacy and oxytocin augmentation, if necessary, would be indicated.