Understanding Labor Onset & Per Vaginal Examination
Comprehensive Nursing Guide for Assessment and Management
Introduction
Labor assessment is a critical skill for obstetric nurses and midwives. Understanding the onset of labor and performing accurate per vaginal examinations enables healthcare providers to make informed decisions about labor management and ensure optimal outcomes for both mother and baby. This comprehensive guide explores the physiological process of labor onset, signs and symptoms, and the technique and interpretation of per vaginal examinations.
Table of Contents
Physiology of Labor
Labor is a physiological process characterized by regular uterine contractions leading to progressive cervical dilation and effacement, ultimately resulting in the delivery of the fetus, placenta, and membranes. The precise trigger for labor onset remains incompletely understood, but several factors contribute to this complex process.
Hormonal Factors in Labor Onset
| Hormone | Role in Labor Assessment |
|---|---|
| Estrogen | Increases myometrial sensitivity to oxytocin; increases prostaglandin production |
| Progesterone | Maintains uterine quiescence during pregnancy; decreases before labor |
| Oxytocin | Stimulates uterine contractions; increases in active labor |
| Prostaglandins | Induce cervical ripening and effacement; stimulate uterine contractions |
| Cortisol | Fetal cortisol increases before labor, stimulating placental hormone shifts |
The transition from pregnancy to labor involves a complex interplay of maternal, fetal, and placental factors. The maternal hypothalamic-pituitary axis, fetal hypothalamic-pituitary-adrenal axis, and placental endocrine functions all contribute to labor assessment and initiation.
Key Point:
The estrogen-progesterone ratio increases significantly as labor approaches. This shift promotes the synthesis of prostaglandins, increases oxytocin receptors in the myometrium, and enhances gap junction formation between myometrial cells, all facilitating coordinated uterine contractions.
Signs and Symptoms of Labor Onset
Recognizing the signs and symptoms of labor onset is crucial for accurate labor assessment and timely care provision. These signs can be categorized as preliminary signs, prodromal signs, and definitive signs of labor.
Preliminary Signs
- Lightening: The settling of the fetal presenting part into the pelvis, resulting in decreased fundal height. May occur days to weeks before labor in primigravidas, but often only shortly before or during labor in multigravidas.
- Braxton Hicks contractions: Irregular, painless uterine contractions that become more frequent and intense as labor approaches.
- Cervical ripening: Softening and effacement of the cervix, which may begin prior to actual labor onset.
- Increased vaginal discharge: Clear mucus discharge due to increased vaginal secretions from congested cervical vessels.
Prodromal Signs
- Weight loss: 0.5-1.5 kg weight loss in the days preceding labor due to fluid shifts and hormonal changes.
- Surge of energy: Some women experience a burst of energy before labor begins (nesting instinct).
- GI symptoms: Loose stools or diarrhea due to prostaglandin release affecting smooth muscles.
- Backache: Persistent low back discomfort from pelvic ligament relaxation and fetal position changes.
Definitive Signs
Mnemonic: “LABOR”
Among these definitive signs of labor, the most reliable indicators for labor assessment are:
- Regular, painful uterine contractions: Progressively increasing in frequency, duration, and intensity.
- Cervical changes: Progressive dilation and effacement.
- Passage of the mucus plug: Often with bloody show due to capillary rupture in the cervix.
- Rupture of membranes: Can occur before or during labor.
Key Point:
Accurate labor assessment requires evaluation of multiple signs rather than relying on any single indicator. The combination of regular contractions with progressive cervical change is the most reliable indicator of true labor.
True vs. False Labor
Differentiating between true and false labor is a critical aspect of labor assessment. False labor, or Braxton Hicks contractions, can mimic true labor but does not lead to progressive cervical changes or delivery.
| Characteristic | True Labor | False Labor |
|---|---|---|
| Contraction regularity | Regular, progressively increasing in frequency | Irregular, no consistent pattern |
| Contraction intensity | Progressively stronger | Variable, often weak |
| Contraction location | Starts in lower back and sweeps to abdomen | Often felt only in abdomen |
| Effect of walking | Contractions continue or intensify | Contractions may decrease or stop |
| Effect of sedation | Contractions continue | Contractions may cease |
| Cervical changes | Progressive dilation and effacement | No significant cervical changes |
| Bloody show | Often present | Usually absent |
Important Assessment Note:
The definitive distinction between true and false labor requires proper labor assessment through per vaginal examination to determine if cervical changes are occurring. However, unnecessary frequent vaginal examinations should be avoided to reduce infection risk.
Stages of Labor
Labor progresses through distinct stages, each requiring specific nursing assessment and interventions. Understanding these stages is essential for effective labor assessment and management.
First Stage of Labor
The first stage begins with the onset of regular contractions and ends with complete cervical dilation (10 cm). It is divided into three phases:
| Phase | Cervical Dilation | Typical Duration | Contraction Pattern | Key Labor Assessment |
|---|---|---|---|---|
| Latent Phase | 0-3 cm | 6-12 hours (shorter in multiparas) | Every 10-30 min, mild to moderate intensity, 30-45 seconds duration | Assess cervical effacement and station; confirm intact membranes |
| Active Phase | 4-7 cm | 3-6 hours | Every 2-5 min, moderate to strong intensity, 45-60 seconds duration | Assess rate of cervical dilation (~1 cm/hr in primigravidas); evaluate fetal descent |
| Transition Phase | 8-10 cm | 30 min to 2 hours | Every 2-3 min, strong intensity, 60-90 seconds duration | Assess for complete dilation; evaluate maternal coping and identify imminent birth signs |
Second Stage of Labor
The second stage begins with complete cervical dilation and ends with the birth of the baby. Duration varies considerably, typically lasting 30 minutes to 2 hours for primigravidas and 5-30 minutes for multigravidas.
- Contraction pattern: Every 2-3 minutes, lasting 60-90 seconds, strong intensity
- Key assessments: Fetal descent, rotation through the birth canal, maternal pushing effectiveness, perineal distension
- Cardinal movements: Engagement, descent, flexion, internal rotation, extension, external rotation, expulsion
Third Stage of Labor
The third stage begins after the birth of the baby and ends with the delivery of the placenta. Typically lasts 5-30 minutes.
- Signs of placental separation: Cord lengthening, small gush of blood, uterine shape change (globular), and rising of the uterus in the abdomen
- Key assessments: Placental delivery completeness, maternal bleeding, uterine tone
Fourth Stage of Labor
The fourth stage refers to the first 1-2 hours after delivery of the placenta. This is a critical period for maternal stabilization.
- Key assessments: Vital signs, uterine tone and position, lochia amount and character, bladder distension, perineal integrity, maternal well-being
- Frequency of assessments: Every 15 minutes for the first hour, then every 30 minutes for the second hour if stable
Key Point:
Labor assessment must be continuous throughout all stages, with documentation of maternal-fetal status, labor progress, interventions, and responses. The frequency and focus of assessment change with each stage of labor.
Per Vaginal Examination
Per vaginal (PV) examination is a critical component of labor assessment that provides valuable information about labor progress. It should be performed by trained healthcare providers with appropriate indications and thorough infection prevention practices.
Indications for PV Examination
Mnemonic: “EXAMINE”
Equipment Needed
- Clean, disposable gloves
- Sterile gloves (if membranes ruptured)
- Antiseptic solution
- Clean drapes
- Adequate lighting
- Lubricant jelly (use only if membranes intact)
- Absorbent pads
- Waste disposal container
Procedure for Per Vaginal Examination
- Preparation:
- Explain the procedure and obtain consent
- Ensure privacy and dignity
- Position the woman in lithotomy or left lateral position
- Perform hand hygiene and don appropriate gloves
- External assessment:
- Observe external genitalia for any abnormalities
- Note presence of bloody show, amniotic fluid
- Internal examination:
- Gently insert index and middle fingers into the vagina
- Assess cervical position, consistency, effacement, and dilation
- Determine fetal presentation, position, and station
- Assess membrane status (bulging, intact, or ruptured)
- Evaluate pelvic adequacy if relevant
- Post-examination:
- Help the woman to a comfortable position
- Discard used equipment appropriately
- Remove gloves and perform hand hygiene
- Document findings completely
- Communicate findings to the woman and healthcare team
Caution:
Per vaginal examinations should be limited to situations where the information will influence management decisions. The WHO recommends a four-hour interval between routine examinations in normal labor. Unnecessary examinations increase infection risk and maternal discomfort.
Cervical Assessment
Cervical assessment is a fundamental component of labor assessment, providing critical information about labor progress. The cervix undergoes several changes during labor that must be carefully evaluated.
Elements of Cervical Assessment
| Parameter | Description | Assessment Method |
|---|---|---|
| Cervical Dilation | Opening of the cervix measured in centimeters (0-10 cm) | Estimated by feeling the diameter of the cervical os with fingertips |
| Cervical Effacement | Thinning of the cervix, measured as percentage (0-100%) | Assessed by feeling cervical length compared to non-pregnant state |
| Cervical Position | Anterior, mid-position, or posterior | Determined by location of cervix relative to vaginal axis |
| Cervical Consistency | Firm, medium, or soft | Assessed by feeling resistance of cervical tissue |
| Station | Relationship of presenting part to ischial spines (-5 to +5 cm) | Measured by distance of presenting part from ischial spines |
Bishop Score
The Bishop score is a labor assessment tool used to evaluate cervical readiness for labor and predict the success of labor induction. It incorporates five components of cervical assessment.
| Component | 0 Points | 1 Point | 2 Points | 3 Points |
|---|---|---|---|---|
| Dilation | Closed | 1-2 cm | 3-4 cm | ≥5 cm |
| Effacement | 0-30% | 40-50% | 60-70% | ≥80% |
| Station | -3 | -2 | -1, 0 | +1, +2 |
| Consistency | Firm | Medium | Soft | – |
| Position | Posterior | Mid-position | Anterior | – |
Interpretation: A Bishop score ≥8 indicates favorable cervix for labor induction with high likelihood of success. A score ≤6 suggests cervical ripening methods may be needed before induction.
Assessing Fetal Presentation and Position
Determining the fetal presentation and position is crucial for proper labor assessment and management planning.
- Presentation: The body part of the fetus that enters the pelvic inlet first and leads through the birth canal (cephalic, breech, shoulder)
- Position: Relationship of the presenting part to the maternal pelvis (e.g., LOA = Left Occipito-Anterior)
- Key landmarks: Sagittal suture and fontanelles for cephalic presentation; sacrum and anus for breech presentation
Key Point:
Labor assessment through cervical examination requires practice and experience. New practitioners should always verify findings with experienced clinicians until competency is established. Accuracy in cervical assessment directly impacts labor management decisions.
Nursing Care During Labor Assessment
Comprehensive nursing care during labor assessment combines technical skills with compassionate support. The nurse’s role encompasses continuous monitoring, comfort measures, and communication with the multidisciplinary team.
Essential Labor Assessment Parameters
Mnemonic: “MFCP”
Monitoring Frequency During Labor
| Parameter | First Stage (Latent) | First Stage (Active) | Second Stage | Third/Fourth Stage |
|---|---|---|---|---|
| Maternal vital signs | Every 4 hours | Every 1-2 hours | Every 30 minutes | Every 15 min for 1 hour, then every 30 min |
| Contractions | Every 30-60 minutes | Every 30 minutes | Every 15-30 minutes | As indicated |
| Fetal heart rate | Every 1 hour | Every 30 minutes | Every 5-15 minutes | N/A |
| Vaginal examination | As indicated | Every 4 hours* | As indicated* | As indicated |
| Uterine tone | N/A | N/A | N/A | Every 15 min for 1 hour, then every 30 min |
| Lochia | N/A | N/A | N/A | Every 15 min for 1 hour, then every 30 min |
* More or less frequently depending on labor pattern and institutional protocols
Documentation of Labor Assessment
Comprehensive documentation is essential for effective labor assessment and communication. The partogram is a standardized tool that provides a visual representation of labor progress.
- Partogram components:
- Maternal vital signs
- Fetal heart rate
- Contraction frequency and duration
- Cervical dilation and effacement
- Fetal station
- Interventions (oxytocin, analgesia)
- Fluid intake and output
- Medications administered
Supporting Women During Labor Assessment
- Emotional support: Continuous reassurance and presence
- Communication: Clear explanations about findings and progress
- Privacy and dignity: Minimize exposure and ensure respectful care
- Pain management: Both pharmacological and non-pharmacological methods
- Positioning: Encourage position changes to enhance comfort and labor progress
- Hydration and nutrition: Support appropriate intake based on labor stage
- Advocacy: Represent woman’s wishes and preferences to healthcare team
Key Point:
The nurse’s role in labor assessment extends beyond clinical monitoring to include emotional support and advocacy. A balance of technical competence and compassionate care optimizes the birth experience and outcomes.
Special Considerations in Labor Assessment
Certain situations require modified approaches to labor assessment to ensure safety while respecting individual needs.
Premature Rupture of Membranes (PROM)
- Definition: Rupture of membranes before the onset of labor
- Assessment modifications:
- Use sterile gloves for all vaginal examinations
- Minimize number of examinations to reduce infection risk
- Document time of rupture, color, odor, and amount of fluid
- Monitor maternal temperature more frequently
- Assess fetal heart rate patterns for signs of infection or cord compression
Previous Cesarean Delivery
- Assessment focus:
- Careful monitoring of contraction pattern and uterine activity
- Vigilance for signs of uterine rupture (sudden pain, vaginal bleeding, fetal distress)
- Monitor progress closely, as labor should follow normal progress patterns
- More frequent assessment of fetal heart rate pattern
Cultural Considerations in Labor Assessment
- Privacy needs: Some cultures may require female providers only
- Communication style: Consider culturally appropriate ways to discuss intimate examinations
- Birth companions: Some cultures have specific preferences for support persons
- Positioning: Cultural preferences may influence acceptable positions for examination
- Pain expression: Cultural variations in pain expression and coping
Abnormal Labor Patterns
Labor assessment becomes particularly crucial when detecting deviations from normal progress:
| Abnormal Pattern | Definition | Assessment Focus |
|---|---|---|
| Protracted Active Phase | Dilation <1 cm/hr in primipara; <1.5 cm/hr in multipara | Evaluate power (contractions), passage (pelvis), passenger (fetal position) |
| Arrest of Dilation | No cervical change for ≥2 hrs in active phase | Assess contraction strength, fetal position, and pelvic adequacy |
| Arrest of Descent | No fetal descent for ≥1 hr in second stage | Evaluate pushing effectiveness, fetal position, and station |
| Precipitous Labor | Labor lasting <3 hours total | Monitor for fetal distress and maternal perineal trauma |
Caution:
Abnormal labor patterns require careful assessment and consultation with senior obstetric providers. Early recognition through accurate and consistent labor assessment helps prevent complications and optimize outcomes.
Global Practices in Labor Assessment
Labor assessment practices vary across countries and healthcare systems, influenced by resources, cultural contexts, and evidence-based guidelines.
World Health Organization Recommendations
- Intermittent auscultation as the primary method of fetal monitoring in low-risk pregnancies
- Limiting vaginal examinations to every 4 hours in normal labor
- Using the partogram with a 4-hour action line
- Supporting freedom of movement and position during labor
- Ensuring respectful maternity care and informed consent for assessments
Innovative Approaches in Different Countries
| Country/Region | Labor Assessment Practice | Benefit |
|---|---|---|
| Netherlands | Strong midwifery model with minimal interventions in low-risk births | Reduced intervention rates while maintaining safety |
| Sweden | Use of “expectant management” with longer timeframes for normal progress | Decreased cesarean rates for labor dystocia |
| Japan | Integration of traditional practices (abdominal palpation) with modern monitoring | Combines cultural respect with technical assessment |
| Uganda | Community-based assessment by trained traditional birth attendants with clear referral pathways | Increased skilled birth attendance in remote areas |
| UK | Midwife-led birth centers with limited use of technology for low-risk women | Enhanced birth experience with comparable outcomes |
Technological Innovations in Labor Assessment
- Wireless monitoring: Allows freedom of movement during continuous fetal monitoring
- Portable ultrasound: For bedside assessment of fetal position and descent
- Electrohysterography: Non-invasive monitoring of uterine activity
- Artificial intelligence: Pattern recognition in fetal heart rate interpretation
- Telemedicine: Remote labor assessment consultation for rural areas
Key Point:
While global practices in labor assessment vary, the core principles remain consistent: ensuring maternal-fetal safety, respecting the physiological process, limiting unnecessary interventions, and providing woman-centered care with informed consent. The best approaches balance technological assessment with supportive care.
Summary
Labor assessment is a fundamental nursing skill requiring both technical competence and compassionate care. Through careful evaluation of labor onset signs, accurate per vaginal examinations, and continuous monitoring of maternal-fetal well-being, nurses facilitate safe birth experiences and optimal outcomes.
Key aspects of labor assessment include:
- Distinguishing true from false labor
- Recognizing the stages and phases of labor
- Performing skilled per vaginal examinations
- Evaluating cervical changes and fetal descent
- Documenting findings accurately using tools like the partogram
- Providing supportive care throughout the labor process
- Identifying deviations from normal progress requiring intervention
As nurses develop proficiency in labor assessment, they become essential members of the obstetric team, blending clinical excellence with advocacy for women’s preferences and needs during childbirth.
References
- World Health Organization. (2018). WHO recommendations: intrapartum care for a positive childbirth experience. Geneva: World Health Organization.
- Cunningham, F. G., Leveno, K. J., Bloom, S. L., Spong, C. Y., Dashe, J. S., Hoffman, B. L., Casey, B. M., & Sheffield, J. S. (2018). Williams Obstetrics (25th ed.). McGraw-Hill Education.
- American College of Obstetricians and Gynecologists. (2019). ACOG Practice Bulletin No. 205: Vaginal Birth After Cesarean Delivery. Obstetrics & Gynecology, 133(2), e110-e127.
- Downe, S., Gyte, G. M., Dahlen, H. G., & Singata, M. (2013). Routine vaginal examinations for assessing progress of labour to improve outcomes for women and babies at term. Cochrane Database of Systematic Reviews, (7).
- National Institute for Health and Care Excellence. (2017). Intrapartum care for healthy women and babies. Clinical guideline [CG190].
- Oladapo, O. T., Diaz, V., Bonet, M., Abalos, E., Thwin, S. S., Souza, H., Perdoná, G., Souza, J. P., & Gülmezoglu, A. M. (2018). Cervical dilatation patterns of ‘low-risk’ women with spontaneous labour and normal perinatal outcomes: a systematic review. BJOG: An International Journal of Obstetrics & Gynaecology, 125(8), 944-954.
- Simpson, K. R., & Creehan, P. A. (2014). Perinatal nursing (4th ed.). Lippincott Williams & Wilkins.
- Hodnett, E. D., Gates, S., Hofmeyr, G. J., & Sakala, C. (2013). Continuous support for women during childbirth. Cochrane Database of Systematic Reviews, (7).