Labor and Delivery: Cardinal Movements and Fetal Heart Rate Strip Interpretation for Nursing Students

The cardinal movements describe the mechanical sequence by which the fetus passes through the birth canal. Understanding these is essential for recognizing normal labor progression and identifying dystocia. The seven cardinal movements in sequence: 1. Engagement: the presenting part (usually the fetal head) descends into the pelvic inlet. Typically occurs at 34-38 weeks gestation in primigravidas (first-time mothers) or during labor in multigravidas. Assessment: station is measured relative to the ischial spines. 0 station = engagement (head at ischial spines). -1 to -3 = above ischial spines (not engaged). +1 to +3 = below ischial spines. 2. Descent: continued downward movement of the fetus through the pelvic canal. Driven by: contractions, maternal pushing efforts, gravity, and uterine forces. Progress monitored by station change over time. 3. Flexion: as the head descends, it meets the resistance of the pelvic floor. This causes the head to flex further, bringing the chin to the chest. Flexion reduces the presenting diameter from occipitofrontal (larger) to suboccipitobregmatic (smaller — 9.5 cm), allowing easier passage. 4. Internal rotation: as the head continues to descend, it rotates to align with the ischial tuberosities. Typical rotation: occiput moves from transverse to anterior position (45° rotation). This aligns the long axis of the fetal head with the long axis of the pelvic outlet. 5. Extension: once the fetal head reaches the perineum, it must extend to pass under the pubic symphysis. The occiput pivots beneath the pubic arch while the head extends upward, delivering the face as the chin, mouth, nose, and eyes sweep past the perineum. 6. External rotation (restitution): after the head is delivered, it rotates back to its original alignment. The shoulders rotate 45° internally to align anteroposterior, which causes the head to rotate externally. This positions the fetus for shoulder delivery. 7. Expulsion: first the anterior shoulder delivers under the pubic arch, then the posterior shoulder clears the perineum. The rest of the body follows rapidly. Memory aid (first letters): Every Decent Family In Every Room Expels — Engagement, Descent, Flexion, Internal rotation, Extension, External rotation, Expulsion. Variations requiring intervention: - Arrest of descent: no progress in descent for 2+ hours - Deflexion (occiput posterior, face presentation): abnormal, often prolonged labor - Shoulder dystocia: anterior shoulder fails to rotate or deliver after head birth — obstetric emergency - Nuchal cord: umbilical cord wrapped around neck — may require reduction or cutting

FHR monitoring produces two tracings on the paper: the top line shows fetal heart rate over time, and the bottom line shows uterine contractions. Interpretation starts with baseline. Baseline FHR calculation: - Mean rate over 10-minute window, excluding accelerations and decelerations - Round to nearest 5 bpm - Must be observed for minimum 2 minutes within the 10-minute window Normal baseline: 110-160 bpm (term gestation). Baseline variations: Tachycardia (baseline > 160 bpm for > 10 min): - Causes: maternal fever, fetal infection, fetal hypoxia, maternal anxiety, medications (beta-agonists), fetal anemia - First-line response: position change, hydration, address maternal fever, reassure - Persistent tachycardia with decreased variability: concerning Bradycardia (baseline < 110 bpm for > 10 min): - Causes: maternal hypothermia, fetal head compression, fetal hypoxia, maternal hypotension, uterine hypertonus, cord compression - First-line response: position change, hydration, oxygen, check for cord prolapse, notify provider - Severe bradycardia (< 100 bpm) is emergent Variability: - The beat-to-beat and long-term fluctuations in baseline - Key indicator of fetal well-being - Classification: - Absent: amplitude range undetectable - Minimal: amplitude ≤ 5 bpm - Moderate: amplitude 6-25 bpm (reassuring) - Marked: amplitude > 25 bpm Reduced variability often indicates: - Fetal sleep (normal, lasts 20-40 min typically) - Maternal medication effects (narcotics, anesthesia, magnesium) - Fetal hypoxia (concerning if persistent) - Fetal acidemia - Abnormal fetal heart function Key point: moderate variability is the most reassuring sign of fetal well-being. Absent variability is concerning — requires prompt evaluation.

Periodic changes are deviations from baseline associated with contractions or fetal movement. Accelerations: - Abrupt increase in FHR of at least 15 bpm above baseline - Lasts at least 15 seconds but less than 2 minutes - Indicates fetal well-being and intact autonomic nervous system - Usually associated with fetal movement - Reassuring finding - Common cause of decreased accelerations: fetal sleep (usually transient) Decelerations (three types based on timing relative to contractions): Early decelerations: - Gradual onset (≥ 30 seconds to nadir) - Nadir coincides with peak of contraction (mirror image of contraction shape) - Usually shallow (10-20 bpm decrease from baseline) - Caused by FETAL HEAD COMPRESSION - NOT associated with hypoxia - Usually seen in late first and second stages of labor as head compresses - REASSURING — typically no intervention needed Late decelerations: - Gradual onset (≥ 30 seconds to nadir) - Nadir occurs AFTER peak of contraction - Shape: delayed repetitive pattern with uniform recurrence - Indicates UTEROPLACENTAL INSUFFICIENCY - Caused by: maternal hypotension, epidural-related hypotension, placental abruption, uterine hypertonus, maternal anemia - CONCERNING — requires intervention - Nursing priorities: left side position, IV fluid bolus, oxygen 10 L/min non-rebreather, discontinue oxytocin, notify provider Variable decelerations: - Abrupt onset (< 30 seconds to nadir) - V, U, or W-shaped appearance - Variable in timing, duration, and amplitude - Caused by UMBILICAL CORD COMPRESSION - Can become concerning if frequent, deep, or prolonged - Nursing priorities: position change (left side, right side, knee-chest if severe), IV fluid bolus, oxygen, notify provider, check for cord prolapse by vaginal exam Prolonged deceleration: - Decrease in FHR of ≥ 15 bpm below baseline - Lasts longer than 2 minutes but less than 10 minutes - Serious finding — requires prompt intervention - If > 10 min, considered a baseline change (bradycardia) Recurrent vs intermittent: - Recurrent: ≥ 50% of contractions associated with decelerations - Intermittent: < 50% - Recurrent late or variable decelerations more concerning than intermittent

The National Institute of Child Health and Human Development (NICHD) three-tier system standardizes FHR interpretation and clinical response. Category I (normal): All of the following: - Baseline 110-160 bpm - Baseline variability: moderate - Accelerations: present or absent (either is acceptable) - Late or variable decelerations: absent - Early decelerations: may be present or absent Strong predictor of normal fetal acid-base status. No intervention needed beyond routine care. Category II (indeterminate): Any FHR tracings not categorized as I or III. Requires evaluation, continued surveillance, and possibly intervention. Most FHR tracings fall here during active labor. Examples of Category II: - Baseline tachycardia or bradycardia - Minimal variability - Absent variability without recurrent decelerations - Variable or late decelerations in some contractions - Prolonged decelerations (2-10 min) - Marked variability (25+ bpm) Interpretation: neither reassuring nor definitively abnormal. Requires nursing and provider evaluation, continued close monitoring, and intervention for specific findings. Category III (abnormal): Either: - Sinusoidal pattern (undulating wave-like FHR), OR - Absent baseline variability with any of: recurrent late decelerations, recurrent variable decelerations, or bradycardia Strongly predicts abnormal fetal acid-base status. Requires immediate intervention. Delivery may be indicated if tracing doesn't resolve with interventions. Interpretation framework (ask these questions systematically): 1. What is the baseline? (Tachycardia, bradycardia, or normal?) 2. What is the variability? (Absent, minimal, moderate, or marked?) 3. Are there accelerations? (Present? Frequency?) 4. Are there decelerations? (Early, late, variable, prolonged?) 5. What is the overall category (I, II, or III)?

Interventions for Category II (most common in practice): If minimal/absent variability: - Position change (left lateral typically) - IV fluid bolus (500-1000 mL normal saline or lactated Ringer's) - Oxygen 10 L/min non-rebreather - Check and address maternal vital signs - Decrease or stop oxytocin if being used - Notify provider - Continue monitoring for improvement If variable decelerations: - Position change: left side first, then right side if not improved, knee-chest if severe - IV fluid bolus - Oxygen - Vaginal exam to rule out cord prolapse (especially if sudden onset or severe) - Discontinue oxytocin if being used - Notify provider If late decelerations: - Position change to left lateral - IV fluid bolus - Oxygen 10 L/min - Address maternal hypotension (common cause with epidural) - Discontinue oxytocin - Prepare for potential cesarean if pattern persists - Notify provider immediately Interventions for Category III: - All of the above measures simultaneously - Immediate provider notification (not just informing — urgent response needed) - Prepare for immediate cesarean delivery - Possible amnioinfusion if variable decelerations - Rapid delivery if tracing doesn't improve Common nursing priorities during concerning tracings: - Never leave the patient alone during Category II or III - Document each intervention and response with timestamps - Anticipate orders for cesarean delivery or fetal scalp stimulation - Support patient and family with clear, calm communication - Prepare delivery equipment and notify NICU team if neonatal resuscitation likely Documentation essentials: - Exact time of tracing change - Description of change (include baseline, variability, periodic changes) - Interventions performed with time stamps - Maternal vital signs before and after intervention - Patient response - Provider notification: who, when, response - Any medication changes (stopping oxytocin, etc.) Remember: interventions during labor focus on restoring fetal oxygenation. All interventions aim to improve placental perfusion (fluid, position, oxygen) or reduce uterine activity (stopping oxytocin).