C-EFM cheat sheet

Fetal oxygen delivery = uterine blood flow × maternal arterial O2 content × placental transfer efficiency; a fall in any factor lowers fetal PaO2 before pH changes.

Umbilical vein carries the most oxygenated fetal blood (approx. 80% saturation) toward the ductus venosus and inferior vena cava; umbilical arteries carry deoxygenated blood back to the placenta.

Fetal hemoglobin (HbF) has higher O2 affinity than adult hemoglobin; the leftward-shifted dissociation curve maintains saturation at low fetal PaO2 (approx. 25-30 mm Hg).

Fetal cardiac output is distributed with brain, heart, and adrenals prioritized; peripheral and pulmonary vasoconstriction during hypoxemia produces the brain-sparing effect.

Uterine blood flow is not autoregulated and falls with maternal hypotension, strong sustained contractions, and alpha-adrenergic vasoconstriction; flow is pressure-dependent.

Maternal supine position compresses the inferior vena cava and aorta, reducing venous return and uterine perfusion; left lateral displacement relieves aortocaval compression.

Fetal baseline heart rate is set by intrinsic sinoatrial pacemaker activity modulated by parasympathetic tone; vagal maturation across gestation lowers the baseline.

Maternal hyperventilation in labor raises PaO2 but lowers PaCO2, shifting the maternal oxyhemoglobin curve left and mildly reducing placental CO2 transfer; pain and anxiety amplify this.

Ultrasound Doppler cardiotocography detects fetal heart motion and calculates rate from Doppler shift; it cannot distinguish maternal from fetal signal without concurrent maternal pulse verification.

Fetal spiral electrode records the fetal ECG directly and requires ruptured membranes, adequate cervical dilation, and a presenting part accessible for attachment.

Maternal pulse artifact is suspected when the recorded rate matches the maternal heart rate; confirm by palpation or pulse oximetry and reposition the transducer.

Half-count artifact doubles the true rate (e.g., 75 bpm displayed as 150 bpm) when the autocorrelation algorithm locks onto every other beat; verify with auscultation.

External tocodynamometry detects contraction frequency and approximate duration but not intensity; it is affected by maternal body habitus and transducer position.

Intrauterine pressure catheter measures amplitude in mm Hg; Montevideo units = sum of peak amplitudes above baseline over a 10-minute window.

Intermittent auscultation requires a fetoscope or Doppler with counting for 60 seconds after a contraction, at intervals set by risk status and stage of labor.

Telemetry and central monitoring extend surveillance during ambulation; signal loss prompts maternal repositioning, transducer adjustment, or gel replacement before assuming fetal compromise.

Baseline rate is the mean rounded to 5 bpm over a 10-minute window, requiring at least 2 minutes of interpretable tracing; normal is 110-160 bpm.

Tachycardia is a baseline above 160 bpm for at least 10 minutes; bradycardia is below 110 bpm for at least 10 minutes.

Variability is the amplitude of fluctuations from the baseline: absent, minimal (undetectable to 5 bpm), moderate (6-25 bpm), or marked (more than 25 bpm).

Accelerations at 32 weeks or later: at least 15 bpm above baseline lasting at least 15 seconds; before 32 weeks: at least 10 bpm for at least 10 seconds.

Early decelerations mirror contractions with gradual onset and return, are vagally mediated head compression, and are considered benign.

Variable decelerations are abrupt drops of at least 15 bpm lasting at least 15 seconds but under 2 minutes, caused by umbilical cord compression.

Late decelerations are gradual, begin after the contraction peak, and return after the contraction ends; they reflect uteroplacental insufficiency.

Prolonged deceleration lasts at least 2 minutes but under 10 minutes; a deceleration of 10 minutes or more is a change in baseline.

Sinusoidal pattern is a smooth undulating baseline of 3-5 bpm at 3-5 cycles per minute lasting at least 20 minutes, associated with fetal anemia.

Normal labor frequency is typically 2-5 contractions in 10 minutes; tachysystole is more than 5 contractions in 10 minutes averaged over 30 minutes.

Resting tone between contractions allows intervillous perfusion; a baseline above 20-25 mm Hg suggests inadequate relaxation or catheter malposition.

Montevideo units of 200 or more in 10 minutes generally indicate adequate uterine activity in spontaneous labor; values are not predictive of progress in every patient.

Contraction duration is measured from onset to offset; typical active-labor contractions last 45-80 seconds.

Coupling refers to contractions occurring in pairs without adequate relaxation between them; it can impair fetal oxygenation.

Tachysystole is classified with or without fetal heart rate decelerations; the presence of decelerations changes management urgency.

Uterine hyperstimulation describes excessive contraction frequency, duration, or tone with nonreassuring fetal status; management includes reducing or stopping oxytocin and tocolysis per protocol.

External palpation and tocodynamometry cannot quantify intensity; only intrauterine pressure catheters or clinical assessment estimate amplitude in mm Hg.

Nonstress test is reactive with at least 2 accelerations meeting gestational-age criteria within 20 minutes; up to 40 minutes may be allowed before calling it nonreactive.

Contraction stress test uses at least 3 contractions in 10 minutes; a negative test shows no late decelerations, and a positive test shows late decelerations with at least half of contractions.

Biophysical profile scores 5 components at 2 points each: fetal breathing, movement, tone, amniotic fluid volume, and nonstress test; 8 or 10 is generally reassuring.

Modified biophysical profile combines a nonstress test with amniotic fluid index; an amniotic fluid index of 5 cm or less is oligohydramnios.

Amniotic fluid volume reflects fetal urine output and placental perfusion; maximum vertical pocket of 2 cm or less defines oligohydramnios in many protocols.

Doppler velocimetry of the umbilical artery shows absent or reversed end-diastolic flow in worsening placental insufficiency and is used in growth-restricted fetuses.

Gestational age affects test interpretation: reactivity and biophysical components mature at different rates, so criteria differ before 32 weeks.

A nonreactive nonstress test requires further evaluation such as a biophysical profile or contraction stress test rather than automatic delivery.

Intrauterine resuscitation measures include maternal left lateral positioning, intravenous fluid bolus, oxygen per unit protocol, discontinuation of oxytocin, and vaginal examination to check for cord prolapse.

Oxytocin infusion requires incremental titration, continuous fetal monitoring, and immediate discontinuation when tachysystole or nonreassuring patterns occur.

Amnioinfusion is used for recurrent variable decelerations from cord compression and for thick meconium; it instills warmed saline through an intrauterine catheter.

Tocolytic therapy such as terbutaline may be used for uterine hyperstimulation with nonreassuring fetal status, with attention to maternal heart rate and glucose.

Operative vaginal delivery and cesarean birth are indicated for category III tracings unresponsive to intrauterine resuscitation, with urgency matched to the pattern.

Shoulder dystocia maneuvers include McRoberts position, suprapubic pressure, rotational maneuvers, and delivery of the posterior arm; fundal pressure is avoided.

Delayed cord clamping and immediate newborn assessment follow delivery; documentation of Apgar scores at 1 and 5 minutes is standard.

Epidural analgesia can cause maternal hypotension and fever, both of which affect fetal heart rate interpretation and require monitoring.

Documentation of fetal heart rate should include baseline, variability, accelerations, decelerations, contractions, and any interventions with responses and times.

NICHD three-tier category system: Category I is normal with moderate variability and no late or variable decelerations; Category III includes absent variability with recurrent late or variable decelerations, bradycardia, or sinusoidal pattern.

Category II encompasses all tracings not meeting Category I or III criteria and requires continued surveillance and evaluation.

Chain-of-communication tools such as SBAR structure reports of nonreassuring tracings with objective data and a clear request for bedside evaluation.

Informed consent discussions include benefits, risks, and alternatives for interventions such as cesarean birth, operative delivery, and induction.

Nursing scope includes independent interpretation of tracings, initiation of intrauterine resuscitation within protocol, and escalation to the provider.

Event timing should be recorded contemporaneously with clock synchronization across devices to support accurate review.

Quality review of adverse outcomes uses standardized terminology such as that from NICHD to reduce miscommunication among clinicians.