Abnormal Labor

Earn CME/CE in your profession:


Continuing Education Activity

Physicians, advanced practice nurses, nursing personnel, and midwives must be aware of what constitutes normal versus abnormal labor. Without proper skills and strategies, appropriate management cannot occur, and poor outcomes become likely for birthing mothers and their neonates. Discerning different types of abnormal labor will allow for proper management. This will decrease morbidity and mortality and improve patient outcomes. This activity characterizes normal versus abnormal labor and encourages the usage of protocols specific to the facility in which the labor is occurring. This activity highlights the critical role of the interprofessional birth team in providing optimal care and counseling to the birthing mother and her infant.

Objectives:

  • Describe what happens in each state of normal labor.
  • Identify the abnormalities that can be picked up on a fetal heart rate strip.
  • Explain how the uterine activity is assessed and identify the target number of contractions and the target duration of each contraction during normal labor.

Introduction

Normal labor is characterized by regular and painful uterine contractions that conclude in progressive labor. A discussion on abnormal labor patterns is reviewed as abnormalities of the first stage (cervical dilation to complete cervical dilation) and the second stage (descent of the presenting part leading to delivery of the baby). The third stage of labor describes the expulsion of the placenta. An overview of labor abnormalities encompasses all the stages of labor. First and second-stage abnormalities are described either as protraction disorders (which means that delivery is progressing but is lower than normal) or as arrest disorders (complete cessation in progress).  Abnormal third-stage labor meriting intervention is placenta retention beyond 30 minutes, as most third stages are concluded within the first 10 to 20 minutes of delivery.[1]

Normal labor is characterized by regular and painful contractions that conclude in delivering the fetus and placenta.  Labor is divided into three stages and subsequent phases within each stage:

  • First Stage: 0-10 cm
    • Latent phase
    • Active phase
  • Second Stage: decent of presenting part leading to the delivery of the fetus
    • Latent (complete cervical dilation to the onset of active maternal expulsive efforts)
    • Active (beginning of active maternal expulsive efforts to the expulsion of the fetus)
  • Third Stage: placental expulsion

Abnormal labor patterns in the first and second stage are defined as either protraction or arrest disorders. Protracted labor stages indicate that labor is progressing but at a slower pace than expected. Arrest disorders indicate the complete cessation of the progress of labor.  Abnormal third-stage labor warrants intervention when the placenta is retained > 30 minutes. The following criteria should be kept in mind when labeling the labor as 

First Stage Protraction and Arrest

Latent Phase

Protraction:

  • In nulliparas women: Not entered the active phase by 20 hours after onset of the latent phase.
  • In multiparas women: Not entered the active phase by 14 hours after the onset of the latent phase.

Arrest: Due to its slow progression, latent phase arrest is not considered a clinical entity.

Active Phase

Protraction: Women at ≥6 cm dilation, dilating less than approximately 1 to 2 cm/hour

Arrest: Cervical dilation ≥6 cm in a patient with ruptured membranes and

  • No change in the cervix for ≥4 hours despite adequate contractions (defined as >200 Montevideo units [MVU])

  • No change in the cervix for ≥6 hours with inadequate contractions

Second Stage Protraction

There is no appropriate length defined for the diagnosis. However, the following criteria can be utilized in the presence of favorable maternal and fetal condition:

  • For nulliparous women: More than four hours for the second stage or three hours of pushing.
  • For multiparous women: More than three hours for the second stage or two hours of pushing.

Etiology

The normal progression of labor requires the four "Ps," representing power from uterine contractions, adequate bony maternal pelvis as the passage, and finally, the fetus as a passenger presenting itself in a favorable presentation. The size of the fetus and the capacity of the maternal pelvis are tested as uterine contractions provide propulsion. A deficiency in the uterine contractions is addressed easily with the judicious use of oxytocin. However, labor abnormalities due to unfavorable fetal pelvic dynamics lead to true dystocia requiring a cesarean delivery.[2]

Risk Factors Associated with Abnormal Labor

Hypocontractile uterus 
Older maternal age
Long cervical length at mid-pregnancy
Pregnancy-related complications
Macrosomia
Obesity
Neuraxial anesthesia
Nonreassuring fetal heart rate pattern
Pelvic contraction
Non-occiput anterior position
Nulliparity
Short stature (less than 150 cm)
The high station at full dilation
Chorioamnionitis
Post-term pregnancy
Bandl's ring

Epidemiology

The trend toward more cesarean sections in the developed countries has drawn attention to initiatives to minimize primary cesarean sections. In this regard, guidelines have been developed to guide more conservative management of the first and second stages of labor abnormalities (Obstetric care consensus: safe prevention of the primary cesarean delivery-ACOG and SMFM, March 2014). After delivery of the baby, the third stage of labor opens the risk for postpartum hemorrhage leading to blood transfusions and maternal morbidity. In the United States, the rate of postpartum hemorrhage increased from 26% from 1994 through 2006, primarily due to increased risks of uterine atony. However, the maternal motility from postpartum obstetric hemorrhage has decreased since the late 1980s to a little more than 10% of the total maternal modality in 2009. Increased and appropriate use of blood transfusions, as well as surgical approaches such as peripartum hysterectomy and compression sutures, have contributed favorably to this statistic.[3]

Pathophysiology

Friedman originally established the labor curve for the first stage of labor; however, it has since been contemporized by Zhang et al. Using recent reference graphs, this stage of labor is not diagnosed until 6 cm cervical dilation. Before diagnosing the arrest of cervical dilation in the first stage of labor, allow 4 hours to progress under adequate uterine activity (with oxytocin as necessary), but for no more than 6 hours.[4] Before 6 cm dilation, the latent phase has a variable duration. It is best to defer amniotomy or neuraxial anesthesia, which brings a commitment to delivery and limits the scope of conservative management. In the second stage of labor, in the absence of neuraxial anesthesia, the nulliparous abdomen may be allowed to push for at least 3 hours. When an epidural is used, an additional 1 hour is provided.  Additionally, voluntary pushing in the second stage in women with an epidural may be allowed when the station of the fetal head is at or below the ischial spines.[5]

Histopathology

Usually, histopathology is used for scenarios where postpartum hemorrhage has occurred. When a hysterectomy is performed for postpartum hemorrhage, the histopathology may return consistent with morbidly adherent placenta such as placenta accreta, increta, or percreta. On occasion, the placental histopathology may return as chorioamnionitis (with our without funisitis), which may be associated with postpartum atony leading to hemorrhage.[6]

Toxicokinetics

Oxytocin is a key pharmacologic agent in the correction of abnormal labor patterns. Although oxytocin's first clinical usage was described in 1906 for postpartum hemorrhage, its molecular structure remained elusive until 1955, and 1 year later, it became commercially available. Exogenous oxytocin responsiveness typically commences at 20 weeks and improves with advancing gestational age until 34 weeks, when it appears to stabilize.[7] The next peak in its sensitivity occurs in labor, which occurs primarily due to the recruitment of myometrial oxytocin receptor binding sites and receptor activation based on elevating intracellular calcium. During spontaneous labor, the blood oxytocin concentration remains stable; however, the responsiveness increases. Oxytocin has a short plasma half-life between 3 to 6 minutes. It is shown that oxytocin takes approximately 40 minutes to reach a steady-state of plasma concentration; however, clinically, it could be adjusted every 30 minutes. Oxytocin is utilized as a continuous intravenous administration using an infusion pump. This allows continuous, precise control of the dosage. Standard institutional protocols are required to minimize adverse oxytocin administration. Of note, oxytocin-induced myometrial receptor desensitization has been demonstrated in animals; its clinical relevance is unknown. As placental perfusion occurs between contractions tachysystole (six or more contractions in a 10-minute window averaged over 10 minutes), it should be avoided as it may impact fetal condition if uncorrected.  Maternal hyponatremia occurs only in extended exposures to a high oxytocin dose, especially if administered in hypotonic solutions. This is based on its structure is similar to vasopressin in some regard, and thus oxytocin cross-reacts with the renal vasopressin receptors. Hypotension has been shown to occur with bolus IV administrations.[8]

History and Physical

Symptoms for the onset of preterm labor are reviewed, including a history of contractions that are progressively stronger and any history of leakage of fluid or passage of a mucous plug. Asking about recent vaginal bleeding is always a significant inquiry to exclude concerns for placental abruption. At admission to labor and delivery, prenatal records and obstetric history should be reviewed because these optimally inform the provider of the best intrapartum obstetric care. This care includes the determination of the static gestational age. An abdominal examination is a key component of an obstetric exam as it provides an estimated fetal weight of the fetus and informs the provider of the fetal presentation and the descent of the presenting part into the pelvis. The continuous monitoring of the external fetal heart rate provides insight into fetal well-being. A manual vaginal exam to evaluate maternal bony pelvis capacity and cervical dilation, as well as fetal pelvic dynamics, occurs at intervals.

Evaluation

The uterine activity is assessed by external tocometry and targeted at 3 to 5 contractions in the 10-minute window. The contractions should last 30 to 40 seconds to be effective. Internal intrauterine pressure assessment using a catheter could be utilized, in which case marked medial units are used and targeted at more than 200 Montevideo units in a 10-minute window. The monitoring of uterine contractions should be continuous during labor. The assessment of the fetal heart rate could be performed utilizing external or internal fetal heart rate monitoring.  An alternative is fetal heart rate auscultation every 15 minutes in the first stage of labor and after each contraction during the second stage of labor. In the interpretation of the fetal heart rate strip millimeters considered are baseline viability, basal heart rate, cardiac accelerations or decelerations, endocrine activity.  Strip abnormalities are characterized based on consideration of the above parameters.

Treatment / Management

The obstetric partogram is a composite graphic record of labor progress. Along with documentation of essential obstetric vital signs, it is used in developing confluent areas to control intrapartum care. The World Health Organization (WHO) recognizes this status as useful labor management that adequately draws attention to excessively prolonged labor.[9] Partogram has increasingly fallen out of use.

Most labor and delivery units will have an established protocol for the administration of oxytocin that entails the administration of the proper medication and dosage, as well as criteria for an incremental increase as clinically warranted. The protocols also include monitoring maternal and fetal vital signs, as well as the atria, for discontinuation of the medication in the event of concern for tachycardia systole all fetal well-being. Such protocols allow collaborative care between the nursing staff and the obstetrician.

Protracted First Stage

Latent phase:

  • This phase can be prolonged for many hours and even days, hence the decision to admit the patient depends on various factors, including status of cervix, emotional and psychological state of the patient, associated complications, tolerance to pain, as well as the distance from hospital and availability of bed. Therefore, it is imperative to discuss the options in detail with the patient.
  • Those admitted to the hospital can be provided therapeutic rest with opioids and sedatives. Morphine, the drug of choice, is administered at a dose of 5 to 10 mg intramuscularly and intravenously simultaneously, with a maximum total dose of 20 mg. Two commonly prescribed agents at home are zolpidem (5 mg orally) and secobarbital (100 mg orally).
  • The women who are well rested can be administered oxytocin with or without amniotomy and/or epidural anesthesia.
  • Prostaglandins, although routinely used for cervical ripening and induction of labor, have not been studied as a therapy for women with a long latent phase.

Active phase:

  • For women in the active phase of the first stage, with cervical dilatation ≤1 cm over two hours, oxytocin is administered followed by amniotomy. However, when the head is high and not well applied to the cervix, amniotomy is delayed after oxytocin for about four to six hours.
  • A high-dose oxytocin regimen is used, regardless of parity, except in women who have had a previous cesarean delivery.
  • If there has been no cervical change after four hours of adequate (>200 Montevideo units) uterine contractions or six hours without adequate uterine contractions, with reassuring fetal and maternal status, it is advisable to proceed with cesarean delivery.
  • However, if labor is still progressing, either slowly or normally, oxytocin administration is continued.

Protracted Second Stage

  • Oxytocin augmentation is begun for minimal (ie, <1 cm) or absent descent after 60 to 90 minutes of pushing and less frequent uterine contractions.
  • In the absence of epidural anesthesia, nulliparous women can push for at least three hours and multiparous women for at least two hours before considering operative intervention. As long as the fetus continues to descend and/or rotate to a favorable position for spontaneous vaginal delivery and the fetal heart rate pattern is reassuring, any form of operative intervention should be delayed.
  • In women who have epidural anesthesia, an additional hour of pushing on a case-by-case basis should be allowed before considering operative intervention.
  • Immediate operative intervention (vaginal/cesarian section) is indicated for fetuses with category III fetal heart rate tracings, regardless of the progression of labor.

Differential Diagnosis

  • Amnionitis

  • Anembryonic pregnancy incomplete abortion
  • Cervical stenosis

  • Ectopic pregnancy
  • Embryonic demise
  • Gestational trophoblastic disease
  • Malpresentation

  • Myomas

  • Subchorionic hemorrhage
  • Uterine bands abnormality
  • Uterine müllerian abnormality

Complications

Prolonged labor can result in the following complications for the mother:

  • Operative vaginal delivery
  • Sphincter Injury
  • Perineal lacerations
  • Cesarean delivery
  • Urinary retention
  • Postpartum hemorrhage
  • Chorioamnionitis
  • Endometritis

Consultations

  • Family practitionerGynecologist/obstetrician
  • Midwives
  • Nurse Practitioners

Deterrence and Patient Education

Abnormal labor can be a daunting experience for women, especially during the first birth. However, patients must be aware that they can be managed both at home and at a maternity care clinic/hospital, depending on the stage and associated risk factors. As the labor progresses, the practitioners may advise rest and analgesia. When the time is due, patients may be under observation to induce labor and/or undergo operative delivery.

Pearls and Other Issues

During labor complications, cesarean deliveries can be a life-saving procedure and may become medically necessary. Cesarean section rates among the nulliparous, singleton, term gestation, and vertex presentation (NSTV) are currently trending in most institutions and states. Diligent management of labor aspires to minimize variation between providers. Management may lower the average cesarean section rates in this population, and this can provide the best opportunity to improve outcomes and reduce costs. In 2012 the baseline NSTV cesarean birth rate was 27% in California, and the most recent rate available in 2015 was 25.6%. As an example, California aspires to reach its target rate of 23.9% or lower by 2022. Racial disparities such as non-Hispanic black women having disproportionately higher cesarean delivery also deserve an inquiry.[10]

Enhancing Healthcare Team Outcomes

The best labor-management requires a coordinated interprofessional effort between trained obstetric nurses, midwives, and providers. Labor is a dynamic process and the decision of practitioners may change depending on the maternal and fetal factors. Since there is always a gray zone in treatment options, t is mandatory to include the patients in their treatment planning. Psychological and emotional support should also be provided, as these women are likely to undergo post-partum blues. Team management may lower the average cesarean section rates and improve outcomes.[Level V]


Article Details

Article Author

Prabhcharan Gill

Article Author

Joshua Henning

Article Editor:

James Van Hook

Updated:

7/19/2021 2:54:14 PM

PubMed Link:

Abnormal Labor

Nursing Version:

Abnormal Labor (Nursing)

References

[1]

Clark SL,Garite TJ,Hamilton EF,Belfort MA,Hankins GD,     [PubMed PMID: 29733840]

[2]

Zhang J,Troendle J,Reddy UM,Laughon SK,Branch DW,Burkman R,Landy HJ,Hibbard JU,Haberman S,Ramirez MM,Bailit JL,Hoffman MK,Gregory KD,Gonzalez-Quintero VH,Kominiarek M,Learman LA,Hatjis CG,van Veldhuisen P, Contemporary cesarean delivery practice in the United States. American journal of obstetrics and gynecology. 2010 Oct     [PubMed PMID: 20708166]

[3]

Stokholm L,Talge NM,Christensen GT,Juhl M,Mortensen LH,Strandberg-Larsen K, Labor augmentation during birth and later cognitive ability in young adulthood. Clinical epidemiology. 2018;     [PubMed PMID: 30538580]

[4]

ACOG Practice Bulletin Number 49, December 2003: Dystocia and augmentation of labor. Obstetrics and gynecology. 2003 Dec     [PubMed PMID: 14662243]

[5]

Zhang J,Troendle JF,Yancey MK, Reassessing the labor curve in nulliparous women. American journal of obstetrics and gynecology. 2002 Oct;     [PubMed PMID: 12388957]

[6]

Langston C,Kaplan C,Macpherson T,Manci E,Peevy K,Clark B,Murtagh C,Cox S,Glenn G, Practice guideline for examination of the placenta: developed by the Placental Pathology Practice Guideline Development Task Force of the College of American Pathologists. Archives of pathology & laboratory medicine. 1997 May     [PubMed PMID: 9167599]

[7]

Wathes DC,Borwick SC,Timmons PM,Leung ST,Thornton S, Oxytocin receptor expression in human term and preterm gestational tissues prior to and following the onset of labour. The Journal of endocrinology. 1999 Apr     [PubMed PMID: 10194538]

[8]

Lee HJ,Macbeth AH,Pagani JH,Young WS 3rd, Oxytocin: the great facilitator of life. Progress in neurobiology. 2009 Jun     [PubMed PMID: 19482229]

[9]

Bailit JL,Dierker L,Blanchard MH,Mercer BM, Outcomes of women presenting in active versus latent phase of spontaneous labor. Obstetrics and gynecology. 2005 Jan     [PubMed PMID: 15625145]

[10]

ACOG Committee Opinion No. 766 Summary: Approaches to Limit Intervention During Labor and Birth. Obstetrics and gynecology. 2019 Feb     [PubMed PMID: 30681540]