Intrapartum fetal heart rate (FHR) monitoring assesses how the fetus tolerates labor. During each contraction, blood flow into the intervillous space of the placenta falls, so the fetus receives less oxygen. A healthy fetus with good placental reserve tolerates this; a fetus with poor reserve develops hypoxemia, then metabolic acidemia.
The FHR reflects fetal oxygenation through the autonomic nervous system
- Moderate variability or accelerations reliably predict the absence of metabolic acidemia at that moment
- Decelerations reflect a reflex (head compression, cord compression) or reduced uteroplacental perfusion
Methods
- Intermittent auscultation (IA) with a handheld Doppler — appropriate for low-risk labor; allows mobility
- External electronic fetal monitoring (EFM): ultrasound transducer (FHR) and tocodynamometer (contraction frequency and duration only — not intensity)
- Internal monitoring: fetal scalp electrode (FSE) and intrauterine pressure catheter (IUPC); require ruptured membranes and some cervical dilation. FSE is avoided with maternal HIV, active genital herpes, and hepatitis B or C when possible, and with suspected fetal bleeding disorders
NICHD definitions (used in the current ACOG 2025 guideline)
| Feature | Definition |
|---|
| Baseline | Mean FHR rounded to 5 bpm over 10 minutes, excluding accelerations, decelerations, and marked variability. Normal 110–160 bpm |
| Tachycardia | Baseline > 160 bpm for ≥ 10 minutes |
| Bradycardia | Baseline < 110 bpm for ≥ 10 minutes |
| Absent variability | Amplitude undetectable |
| Minimal variability | ≤ 5 bpm |
| Moderate variability | 6–25 bpm (normal) |
| Marked variability | > 25 bpm |
| Acceleration | Abrupt rise ≥ 15 bpm for ≥ 15 seconds (≥ 10 × 10 before 32 weeks) |
| Prolonged deceleration | Decrease ≥ 15 bpm lasting ≥ 2 minutes but < 10 minutes (10 minutes or more = baseline change) |
| Recurrent decelerations | Occur with ≥ 50% of contractions in a 20-minute window |
Decelerations — cause and nursing response
| Type | Shape and timing | Cause | Response |
|---|
| Early | Gradual (onset to nadir ≥ 30 seconds); mirror image — nadir coincides with the contraction peak | Head compression (vagal) | None needed — benign |
| Late | Gradual; nadir occurs after the contraction peak; returns after the contraction ends | Uteroplacental insufficiency | Intrauterine resuscitation; notify provider |
| Variable | Abrupt (onset to nadir < 30 seconds), ≥ 15 bpm for ≥ 15 seconds and < 2 minutes; timing varies | Umbilical cord compression | Reposition first; amnioinfusion if recurrent |
| Prolonged | ≥ 2 minutes | Cord prolapse, uterine tachysystole, hypotension, rupture, rapid descent | Vaginal exam, resuscitation, urgent notification |
Memory aid: VEAL CHOP — Variable = Cord compression, Early = Head compression, Accelerations = OK, Late = Placental insufficiency.
Uterine activity
- Normal: 5 or fewer contractions in 10 minutes, averaged over 30 minutes
- Tachysystole: more than 5 contractions in 10 minutes, averaged over 30 minutes — always note whether decelerations are present
- Frequency = start of one contraction to start of the next; duration = start to end of one contraction
- With an IUPC: resting tone normally below about 25 mmHg; adequate labor is often defined as ≥ 200 Montevideo units
Three-tier FHR interpretation system
| Category | Criteria | Meaning |
|---|
| I (normal) | Baseline 110–160, moderate variability, no late or variable decelerations; early decelerations and accelerations may or may not be present | Strongly predicts normal fetal acid–base status; routine care |
| II (indeterminate) | Everything not in Category I or III (e.g., tachycardia, minimal variability, recurrent variables with moderate variability, absence of induced accelerations, prolonged deceleration) | Needs evaluation, surveillance, and intrauterine resuscitation |
| III (abnormal) | Absent variability with recurrent late decelerations, recurrent variable decelerations, or bradycardia; or a sinusoidal pattern | Predicts abnormal acid–base status; resuscitate and prepare for expedited delivery |
Adjunct tests
- Fetal scalp stimulation or vibroacoustic stimulation: an acceleration in response strongly suggests the fetus is not acidemic
- Umbilical cord blood gases after birth document fetal acid–base status (metabolic acidemia: umbilical artery pH < 7.0 and base deficit ≥ 12 mmol/L)
- Amniotic fluid assessment when membranes rupture: meconium-stained fluid may signal fetal stress and increases risk of meconium aspiration
Current ACOG guideline (Clinical Practice Guideline No. 10, 2025)
- Category I: routine intrapartum care
- Category II: attempt intrauterine resuscitation before proceeding to cesarean — maternal position change, IV fluid bolus, reducing or stopping oxytocin or other induction agents, amnioinfusion (recurrent variables), and correcting maternal causes (hypotension, fever)
- Category III: begin resuscitation and expedite delivery if the tracing does not respond
- Amnioinfusion (warmed isotonic saline through an IUPC) is used for recurrent variable decelerations; monitor resting tone and fluid return to avoid uterine overdistension
- Tachysystole with abnormal FHR that persists after stopping oxytocin: a rapid-acting tocolytic (e.g., terbutaline 0.25 mg subcutaneously) may be given
- Routine maternal oxygen is not recommended for Category II or III tracings unless the mother is hypoxic — a change from older teaching that gave 8–10 L/min by face mask for every abnormal pattern
- ST-segment analysis, fetal pulse oximetry, and computerized interpretation alone are not recommended for routine use
Terbutaline safety: maternal tachycardia, palpitations, hyperglycemia, hypokalemia; hold with maternal heart rate above facility limit (often > 120/min) or cardiac disease. Not for prolonged tocolysis (FDA boxed warning).
Listed in priority order.
- Identify and act on abnormal patterns (intrauterine resuscitation)
- Reposition to left or right lateral (or hands-and-knees for variable decelerations)
- Stop oxytocin if running and contractions are excessive or FHR is abnormal
- IV fluid bolus (lactated Ringer's) per protocol; correct hypotension (after epidural, notify anesthesia)
- Perform a vaginal exam to check for cord prolapse, rapid descent, or imminent birth when a sudden prolonged deceleration occurs
- Give oxygen only if the mother is hypoxemic or per facility protocol
- Notify the provider using SBAR; use the chain of command if the response is inadequate
- Assess FHR at required intervals
- IA for low-risk labor (AWHONN): about every 15–30 minutes in active first stage and every 5–15 minutes in second stage, counting the FHR for 30–60 seconds after a contraction while palpating the contraction
- Always assess FHR immediately after rupture of membranes (cord prolapse risk), after amniotomy, vaginal exams, epidural dosing, oxytocin changes, and before and after analgesics
- Ensure accurate data
- Confirm the signal is fetal, not maternal (compare with maternal pulse — maternal heart rate can be recorded as FHR, especially in second stage)
- Reposition the transducer; consider FSE if external tracing is inadequate
- Assess contractions by palpation and the monitor; watch for tachysystole during oxytocin
- Comfort and communication
- Explain monitoring purpose; allow position changes; support the family during emergencies
- Document baseline, variability, accelerations, decelerations, category, uterine activity, interventions, and the provider's response
The nurse interprets the tracing, intervenes, and reports; the decision about mode of delivery belongs to the obstetric provider.
- Explain why the monitor is used and what the sounds and alarms mean; a lost signal is common and does not always mean a problem
- Encourage upright or side-lying positions and avoid lying flat on the back
- Tell the nurse immediately about a gush of fluid, feeling something in the vagina, sudden severe pain, or dizziness
- Reassure that brief changes in heart rate are common and that position changes often correct them
| Red flag | Possible cause |
|---|
| Category III tracing | Fetal metabolic acidemia |
| Sudden prolonged deceleration or bradycardia | Cord prolapse, uterine rupture, placental abruption, maternal hypotension |
| Recurrent late decelerations with minimal variability | Uteroplacental insufficiency |
| Sinusoidal pattern | Severe fetal anemia (fetomaternal hemorrhage, vasa previa rupture) |
| Fetal tachycardia with maternal fever | Intraamniotic infection |
| Tachysystole with decelerations | Oxytocin or prostaglandin effect |
| Thick meconium | Risk of meconium aspiration syndrome |
- Baseline 110–160; moderate variability 6–25 bpm is the best sign of fetal well-being
- Early = head compression (benign); Late = placental insufficiency; Variable = cord compression
- Variable decelerations → change maternal position first; amnioinfusion if recurrent
- Late decelerations → lateral position, stop oxytocin, IV fluids, correct hypotension, notify
- Category III: absent variability + recurrent lates/variables/bradycardia, or sinusoidal
- Tachysystole: > 5 contractions in 10 minutes averaged over 30 minutes
- Routine maternal oxygen is no longer recommended without maternal hypoxia
- Check FHR immediately after membranes rupture
- Distinguish maternal pulse from FHR
- Accelerations after scalp stimulation suggest no acidemia
Country Notes
United States
- ACOG Clinical Practice Guideline No. 10 (October 2025) replaced Practice Bulletin 106 and the 2022 Practice Advisory on oxygen supplementation while keeping the three-tier NICHD system; AWHONN provides nursing standards for IA frequency and fetal monitoring education.
Philippines
- Many public facilities rely on intermittent auscultation with handheld Doppler or fetoscope and a partograph rather than continuous EFM; the same deceleration concepts apply, and abnormal findings require prompt referral or physician notification.