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Diagnosis of Abnormal Labor Last Updated: August 6, 2005 |
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| Synonyms and related keywords: dystocia, prolonged labor, arrest of dilation, arrest of descent, cephalopelvic disproportion, protraction disorder, primary dysfunctional labor, pelvimetry, Montevideo units, MVUs, cesarean section, c-section, cesarean birth, cesarean delivery
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AUTHOR INFORMATION
| Section 1 of 11   |
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| Author: Saju Joy, MD, Fellow, Division of Maternal Fetal Medicine, Department of Obstetrics and Gynaecology, The Ohio State University School of Medicine Coauthor(s): Deborah Lyon, MD, Director, Division of Benign Gynecology, Associate Professor, Department of Obstetrics and Gynecology, University of Florida Health Science Center at Jacksonville |
| Saju Joy, MD, is a member of the following medical societies:
American College of Obstetricians and Gynecologists, and
American Medical Association |
| Editor(s): Robert K Zurawin, MD, Associate Professor, Director of Fellowship Programs, Minimally Invasive Surgery, Department of Obstetrics and Gynecology, Baylor College of Medicine; Chief of Gynecology, Texas Children's Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine;
Richard S Legro, MD, Professor, Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine;
Frederick B Gaupp, MD, Consulting Staff, Department of Family Practice, Assumption Community Hospital;
and Lee P Shulman, MD, Professor of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University; Chief, Division of Reproductive Genetics, Department of Obstetrics and Gynecology, Prentice Women's Hospital, Northwestern Memorial Hospital |
Disclosure
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INTRODUCTION
| Section 2 of 11   |
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Background: In order to define abnormal labor, a definition of normal labor must be understood and accepted. Normal labor is defined as uterine contractions that result in progressive dilation and effacement of the cervix. By following thousands of labors resulting in uncomplicated vaginal deliveries, certain time limits and progress milestones have been identified. Failure to meet these milestones defines abnormal labor, which suggests an increased risk of an unfavorable outcome. Thus, abnormal labor alerts the obstetrician to consider alternative methods for a successful delivery that minimize risks to both the mother and infant.
Friedman's original research in 1955 defined 3 stages of labor. The first stage starts with uterine contractions leading to complete cervical dilation and is divided into latent and active phases. In the latent phase, there are irregular uterine contractions but slow and gradual cervical effacement and dilation. The active phase is demonstrated by an increased rate of cervical dilation and fetal descent. The active phase usually starts at 3-4 cm cervical dilation and is subdivided into the acceleration, maximum slope, and deceleration phases.
The second stage of labor ranges from complete dilation to the delivery of the infant. The third stage of labor involves delivery of the placenta.
See Image 1 for the normal labor curves of both nulliparas and multiparas. See Image 2 for abnormal labor indicators.
Abnormal labor constitutes any findings that fall outside the accepted normal labor curve. However, the authors hesitate to apply the diagnosis of abnormal labor during the latent phase because confusing prodromal contractions for latent labor is easy.
Abnormal labor of the second stage is often a result of problems with one of the 3 P's.
- Passenger (infant size and fetal presentation, eg, in cephalic-occiput anterior or occiput posterior vs breech or transverse)
- Pelvis or passage (size and adequacy of the pelvis)
- Power (uterine contractility)
See Causes. Pathophysiology: A prolonged latent phase may result secondary to oversedation or upon entering labor early with a thickened or uneffaced cervix. It may be misdiagnosed in the face of frequent prodromal contractions. Protraction of active labor is more easily diagnosed and is dependent upon the 3 P's.
The first P, the passenger, may produce abnormal labor because of the infant's size (eg, macrosomia) or from malpresentation.
The second P, the pelvis, can cause abnormal labor because its contours may be too small or narrow to allow passage of the infant. Both the passenger and pelvis cause abnormal labor by a mechanical obstruction, referred to as dystocia.
With the third P, the power component, the frequency of uterine contraction may be adequate, but the intensity may be inadequate. Disruption of communication between adjacent segments of the uterus may also exist, resulting from surgical scarring, fibroids, or other conduction disruption. Whatever the cause, the contraction pattern fails to result in cervical effacement and dilation. Frequency:
- In the US: Of all cephalic deliveries, 8-11% are complicated by an abnormal first stage of labor. Dystocia occurs in 12% of deliveries in women without a history of prior cesarean delivery. Dystocia may account for as many as 60% of cesarean deliveries.
Mortality/Morbidity: Both maternal and fetal mortality and morbidity rates increase with abnormal labor. This is probably an effect-effect relationship rather than a cause-effect relationship. Nonetheless, identification of abnormal labor and initiation of appropriate actions to reduce the risks are matters of some urgency.
History: - Evaluate every pregnant patient who presents with contractions in the labor and delivery suite.
- Any patient in labor is at risk for abnormal labor regardless of the number of previous pregnancies or the seemingly adequate dimensions of the pelvis.
- Plot the progress of any patient in labor, and evaluate it on a labor curve.
Physical: - Upon admission to the labor and delivery suite, determine and document clinical findings.
- Clinical pelvimetry, which is best performed at the first prenatal care visit, is important in order to assess the pelvic type (eg, android, gynecoid, platypelloid, anthropoid).
- Also evaluate the position of the fetal head in early labor because caput and moulding complicate correct assessment as labor progresses.
- The next component is establishing and documenting an estimated fetal weight.
- The physician must also monitor fetal heart rate and uterine contraction patterns and assess fetal well-being.
- The final component includes a cervical examination to determine if the patient is in the latent or active phase of labor.
- By addressing these issues, the physician is aware of the current phase of labor and can anticipate whether abnormal labor from any of the 3 P's will be encountered.
Causes: - The latent phase of labor is defined as the period of time starting with the onset of regular uterine contractions and ending with the onset of the active phase (3-4 cm cervical dilation).
- The prolonged latent phase is defined as exceeding 20 hours in patients who are nulliparas or 14 hours in patients who are multiparas.
- The most common reason for prolonged latent phase is entering labor without substantial cervical effacement.
- Another cause for abnormal labor is power, defined as uterine contractility multiplied by the frequency of contractions.
- Montevideo units (MVUs) refer to the strength of contractions in mm of mercury multiplied by the frequency per 10 minutes as measured by intrauterine pressure transducer.
- The uterine contraction pattern must repeat every 2-3 minutes.
- The uterine contractile force produced must exceed 200 MVUs/10 min for active labor to be considered adequate. For example, 3 contractions in 10 minutes that each reach a peak of 60 mm Hg are 60 X 3 = 180 MVUs.
- An arrest disorder cannot be diagnosed until the patient is in the active phase and the contraction pattern exceeds 200 MVUs for 2 hours with no cervical change.
- Another cause for the abnormal labor could be the pelvis or the size of the passageway inhibiting delivery.
- For example, diagnosing an anthropoid pelvis (ie, a pelvic type that is oval with a vertical long side) alerts the physician to the possibility of the infant presenting in the occiput posterior. As a result, the physician might expect a prolonged labor course.
- A patient who is extremely short or very obese, or who has had prior trauma to the bony pelvis, may also be at increased risk of abnormal labor.
- Finally, abnormal labor could also be secondary to the passenger, the size of the infant, and/or the infant's presentation.
- In addition to problems caused by the differential in size between the fetal head and the maternal bony pelvis, the fetal presentation may include asynclitism or head extension, which compromises the narrowest diameter through the pelvis.
- Fetal macrosomia and other anomalies (including hydrocephalus, encephalocele, fetal goiter, cystic hygroma, hydrops, or anything that increases the size of the infant) are likely to cause deviation from the normal labor curve.
- Low-dose epidural and combined spinal-epidural anesthetics minimize motor block that may contribute to a prolonged second stage. Oversedation has been implicated as prolonging labor in both the latent and active phases.
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DIFFERENTIALS
| Section 4 of 11 |
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Abruptio Placentae
Other Problems to be Considered:
False labor
Premature labor |
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Lab Studies:
- No specific laboratory studies are used to assess abnormal labor.
Imaging Studies:
- X-ray pelvimetry and CT pelvimetry may be helpful to assess the maternal bony pelvis.
- These studies are most often used to reassure clinicians of pelvic adequacy when performing elective vaginal deliveries in breech presentations.
- These studies are not error free because dystocia or abnormal labor can arise from soft tissue obstructions in the pelvic outlet, particularly in women who are obese.
Other Tests:
- The simplest test used to evaluate abnormal labor is to plot the patient's labor progress (cervical dilation vs duration in h) on a labor curve.
- A second test used to address adequate labor is the review of the uterine contraction pattern.
- Most importantly, the fetal heart tracing must be reassuring throughout the labor course.
Procedures:
- Clinical pelvimetry, at a minimum, must address the angles of the spinous processes (convergent, divergent, straight), the bi-ischial diameter (>8 cm), the distance to the sacral promontory from the symphysis pubis (>12 cm), and the relation of the bony pelvis to the fetal head.
- Clinical pelvimetry requires experience and deliberate attention to the question of pelvic adequacy.
- It cannot account for fetal size or strength/frequency of contractions, but in experienced hands, it may reliably identify a pelvis as adequate, borderline, or contracted.
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TREATMENT
| Section 6 of 11 |
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Medical Care: A prolonged latent phase (see Image 2) is not indicative of dystocia in itself because this diagnosis cannot be made in the latent phase. Gabbe and colleagues state the following:
For those in the latent phase, the treatment of choice is rest or sleep for several hours. During this interval uterine activity, fetal status and cervical effacement must be evaluated to determine if progress to the active phase has occurred. Approximately 85% of patients so treated will progress to the active phase. Approximately 10% will cease to have contractions, and the diagnosis of false labor may be made. For the approximately 5% of patients in whom therapeutic rest fails and in patients for whom expeditious delivery is indicated, oxytocin infusion may be used. - If the abnormal labor results from functional dystocia or an abnormal uterine contractility pattern, and oxytocin implementation has not improved the outcome, a beta-blocker may be used.
- Image 4 lists inclusion and exclusion criteria for beta-blocker use.
- Low-dose administration of intravenous propranolol in abnormal labor augmented with oxytocin reduced the need for cesarean delivery, particularly among patients with inadequate uterine contractility.
- Anecdotal reports have stated that simply repositioning the patient frequently relieves a seemingly obstructed labor.
- Although not studied rigorously, there appears to be little harm in this maneuver.
- In theory, it may unseat an asynclitic or malrotated presenting part and allow it to engage in the pelvis more effectively.
Surgical Care: - Amniotomy is often used and is an accepted practice once the patient has reached the active phase of labor. However, this practice is not recommended in the latent phase of labor because it may only serve to increase the risk of intrauterine infection or cord prolapse.
- If one of the arrest or protraction disorders is identified and fails to respond to conservative measures, or if the fetal heart pattern is nonreassuring, expedient delivery is justified; this includes operative vaginal delivery or cesarean delivery as indicated.
Diet: - Most institutions have standing orders that patients in labor have nothing by mouth as a precaution should the need for an emergent cesarean delivery arise.
- Some institutions permit ice chips, and others permit a clear liquid diet.
- If patients have been carefully selected as low risk for labor obstruction, a regular diet may be ordered.
- Pregnant women have delayed gastric emptying, and aspiration is a very serious concern in the event of an anesthetic induction.
Activity: - For patients in labor, remaining active and mobile while in the latent and early active phase is best.
- However, once rupture of membranes has occurred or signs of fetal nonreassurance exist, then bed rest and continuous fetal monitoring is appropriate.
- Some physicians allow ambulation throughout labor as long as the fetal head is well applied (minimizing risk of cord prolapse) and evidence of fetal well-being exists (monitoring for 20 min/h without signs of fetal compromise).
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MEDICATION
| Section 7 of 11 |
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A method called active management of labor is practiced in Ireland. This method is applied to women who are nulliparous with singleton cephalic presentations at term. It involves the use of high-dose oxytocin, with a starting rate of 6 mU/min and increasing by 6 mU/min every 15 min to a maximum of 40 mU/min. The goal is no more than 7 uterine contractions per 15 min. Cesarean delivery is performed if vaginal delivery has not occurred or is not imminent 12 hours after admission or for fetal compromise (diagnosed with fetal scalp pH). Initially, the Irish cesarean delivery rate was quoted at 4.8%, but it has now doubled, which is attributed to widespread use of epidural anesthesia. Other studies using the active management protocol describe similar cesarean delivery rates to that of the low-dose protocol.
Dinoprostone and misoprostol are prostaglandin analogs used to stimulate cervical dilation and uterine contractions; they are pharmacologic alternatives to using laminaria or placing a Foley bulb in the cervix.
Drug Category: Abortifacients -- Oxytocin is the only US Food and Drug Administration (FDA)–approved medication recommended for labor augmentation. Other options include dinoprostone and misoprostol. Drug Name
| Oxytocin (Pitocin) -- Produces rhythmic uterine contractions and can stimulate the gravid uterus. Has vasopressive and antidiuretic effects. Can also control postpartum bleeding or hemorrhage. Has a half-life of 3-5 min, and reaches steady state in approximately 40 min. |
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| Adult Dose | Common protocol: Start infusion at 1-2 mU/min and increase by 1-2 mU/min q30 min; continue until adequate contractions (>200 MVUs/10 min) achieved or (at some institutions) maximum rate of 20 mU/min achieved |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity; pregnant patients with severe toxemia; unfavorable fetal positions; a contracting uterus with hypertonic or hyperactive patterns; labor when vaginal delivery should be avoided such as invasive cervical carcinoma, cord presentation or prolapse, active herpes genitalis, total placenta previa, and vasa previa |
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| Interactions | Pressor effect of sympathomimetics may increase when used concomitantly with oxytocic drugs, causing postpartum hypertension |
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| Pregnancy |
X - Contraindicated in pregnancy |
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| Precautions | An overstimulated uterus can be hazardous to both mother and fetus; hypertonic contractions can occur in a patient whose uterus is hypersensitive to oxytocin, regardless of whether it was administered appropriately; has intrinsic antidiuretic effect that when administered by continuous infusion and patient is receiving fluids by mouth, can cause water intoxication |
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Drug Name
| Misoprostol (Cytotec) -- Prostaglandin analog that causes cervix to thin and dilate and uterus to contract as it does during labor. Not FDA approved for this use. |
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| Adult Dose | 25-50 mcg tab inserted intravaginally (paracervically); may readminister after 4 h if patient reassessment is reassuring (<3 contractions/10 min) |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity; do not administer if >3 uterine contractions/h or in patients with uterine scar (eg, previous cesarean delivery, myomectomy) |
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| Interactions | None reported |
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| Pregnancy |
X - Contraindicated in pregnancy |
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| Precautions | An overstimulated uterus can be hazardous to both mother and fetus; hypertonic contractions can occur; therefore, patient must be under continuous medical supervision; caution when exceeding 150-200 mcg; monitor for tachysystole of uterine contractions (if this occurs, medication should be washed out of vagina with isotonic sodium chloride solution); not FDA approved for this indication |
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Drug Name
| Dinoprostone (Cervidil) -- Prostaglandin E2 causes cervix to thin and dilate and uterus to contract as it does during labor. Do not start oxytocin within 6 h of dinoprostone. |
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| Adult Dose | Gel: 0.5 mg/syringe intracervically or 10 mg vaginal insert placed in posterior vaginal fornix (removed after active labor or after 12 h); reassess cervical change in 4-6 h |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity |
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| Interactions | None reported |
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| Pregnancy |
X - Contraindicated in pregnancy |
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| Precautions | An overstimulated uterus can be hazardous to both mother and fetus; hypertonic contractions can occur; therefore, patient must be under continuous medical supervision; abdominal or stomach cramps, diarrhea, fever, nausea, or vomiting may occur |
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Drug Category: Beta-adrenergic blocking agents -- Another option for abnormal labor secondary to inadequate uterine contractility is a beta-blocker. See Image 4 for inclusion and exclusion criteria.Drug Name
| Propranolol (Inderal) -- Nonselective beta-adrenergic receptor blocker. |
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| Adult Dose | 2 mg IV; repeat one time only in 1 h if no progress observed |
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| Pediatric Dose | Not established |
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| Contraindications | Documented hypersensitivity; uncompensated congestive heart failure; bradycardia, cardiogenic shock; AV conduction abnormalities |
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| Interactions | Coadministration with aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease propranolol effects; calcium channel blockers, cimetidine, loop diuretics, and MAOIs may increase toxicity of propranolol; toxicity of hydralazine, haloperidol, benzodiazepines, and phenothiazines may increase with propranolol |
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| Pregnancy |
C - Safety for use during pregnancy has not been established.
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| Precautions | Beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; withdraw drug slowly and monitor closely |
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FOLLOW-UP
| Section 8 of 11 |
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Complications:
- Maternal infection is a risk, especially when rupture of membranes occurs for more than 18 hours. Administer antibiotics when it appears that this time will be exceeded or for signs/symptoms of chorioamnionitis.
- Fetal compromise can occur from the inability to tolerate labor (eg, uterine hyperstimulation) or infection, and it must be closely evaluated. Fetal heart monitoring often reveals signs of compromise with decelerations, and fetal scalp pH is an option when indicated.
- Probably the most common complication of the medical induction of labor is hyperstimulation of the uterus. If unrecognized and untreated, excessive stimulation of the uterus can result in fetal compromise, cord compression, and uteroplacental insufficiency. Uterine rupture, postpartum uterine atony, and postpartum hemorrhage may occur and are very serious and life-threatening complications.
Prognosis:
- The prognosis of subsequent pregnancies depends on the cause for abnormal labor. For example, if abnormal labor occurs from macrosomia, the next infant may not be macrosomic. However, if the abnormal labor was secondary to a contracted pelvis with a normal-sized or small infant, then the likelihood for a recurrence of abnormal labor is high.
Patient Education:
- The patient must be aware of all risks involved with labor, including the potential for emergent cesarean delivery if the fetus is compromised. Furthermore, inform her of status throughout the labor course, especially if a change in management is anticipated. Counsel patients early in pregnancy that maternal weight gain correlates with fetal weight gain, and excessive gain is a risk factor for abnormal labor.
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MISCELLANEOUS
| Section 9 of 11 |
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Medical/Legal Pitfalls:
- The primary goal in labor is to provide the safest outcome for both mother and infant.
- The primary medicolegal issue in abnormal labor is failure to diagnose.
- Any change from the normal labor curve requires reassessment regarding the 3 P's.
- Once the cause of labor dysfunction is identified, correct it if possible, and closely monitor the labor.
- If the corrective measures are unsuccessful in resolving the abnormal labor, then consider an operative delivery.
- Fetal heart tracing must be reassuring in order to continue with expectant management. However, if fetal compromise exists, anticipate expedited delivery.
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PICTURES
| Section 10 of 11 |
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BIBLIOGRAPHY
| Section 11 of 11 |
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American College of Obstetrics and Gynecology Committee on Practice Bulletins-Ob: ACOG technical bulletin. Dystocia and the augmentation of labor. Number 218--December 1995 (replaces no. 137, December 1989, and no. 157, July 1991). American College of Obstetricians and Gynecologists. Int J Gynaecol Obstet 1996 Apr; 53(1): 73-80[Medline].
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American College of Obstetrics and Gynecology Committee on Practice Bulletins-Ob: ACOG Practice Bulletin Number 49, December 2003: Dystocia and augmentation of labor
. Obstet Gynecol 2003 Dec; 102(6): 1445-54[Medline].
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Creasy RK, Resnik R, Bowes WA: Clinical aspects of normal and abnormal labor. In: Maternal-Fetal Medicine. 4th ed. 1999:543-549.
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Cunningham FG, MacDonald PC, Gant NF: Abnormal labor. In: Williams Obstetrics. 20th ed. Appleton & Lange; 1997:415-434.
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Friedman EA: Primigravid Labor: A graphicostatistical analysis. Obstet Gynecol 1955; 6: 567-589.
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Friedman EA: Labor in Multiparas: A graphicostatistical analysis. Obstet Gynecol 1956; 8: 691-703.
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Gabbe SJ, O'Brien WF, Cefalo RC: Labor and delivery. In: Obstetrics: Normal and Problem Pregnancies. 3rd ed. 1996:378-381.
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Gardberg M, Stenwall O, Laakkonen E: Recurrent persistent occipito-posterior position in subsequent deliveries. BJOG 2004 Feb; 111(2): 170-1[Medline].
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Gifford DS, Morton SC, Fiske M, et al: Lack of progress in labor as a reason for cesarean. Obstet Gynecol 2000 Apr; 95(4): 589-95[Medline].
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Saito M, Kozuma S, Kikuchi A, et al: Sonographic assessment of the cervix before, during, and after a uterine contraction is effective in predicting the course of labor. Obstet Gynecol Surv 2004 Jun; 59(6): 420-1[Medline].
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Sanchez-Ramos L, Quillen MJ, Kaunitz AM: Randomized trial of oxytocin alone and with propranolol in the management of dysfunctional labor. Obstet Gynecol 1996 Oct; 88(4 Pt 1): 517-20[Medline].
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Socol ML, Peaceman AM: Active management of labor. Obstet Gynecol Clin North Am 1999 Jun; 26(2): 287-94[Medline].
Diagnosis of Abnormal Labor excerpt |
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