C-EFM flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fetal hemoglobin affinity

Fetal hemoglobin binds oxygen more avidly than adult hemoglobin, shifting the dissociation curve left and maintaining fetal saturation despite low fetal partial pressure of oxygen.

Uterine blood flow regulation

Uterine perfusion lacks autoregulation and depends on maternal arterial pressure; hypotension, sustained contractions, and vasoconstriction directly reduce flow to the placenta.

Aortocaval compression

Supine positioning compresses the inferior vena cava and aorta, reducing venous return and placental perfusion; left lateral displacement restores cardiac output and fetal oxygenation.

Brain-sparing effect

During fetal hypoxemia, peripheral and pulmonary vasoconstriction redirects cardiac output toward the brain, heart, and adrenals, preserving oxygenation of vital organs.

Fetal baseline heart rate control

Intrinsic sinoatrial pacemaker activity sets the fetal rate, modulated by parasympathetic vagal tone that increases with gestational age and lowers the resting baseline.

Maternal hyperventilation effect

Pain-related hyperventilation raises maternal oxygen and lowers carbon dioxide, shifting the maternal oxyhemoglobin curve left and slightly impairing placental carbon dioxide transfer.

Doppler ultrasound limitations

Doppler cardiotocography detects fetal heart motion but cannot distinguish maternal from fetal signal, so maternal pulse verification is needed when rates appear identical.

Fetal spiral electrode criteria

Direct fetal electrocardiography requires ruptured membranes, sufficient cervical dilation, and an accessible presenting part; it gives accurate rate and beat-to-beat variability.

Half-count artifact

Autocorrelation algorithms sometimes lock onto every other beat, displaying double the true rate; auscultation or pulse verification confirms the actual fetal rate.

External tocodynamometry limits

External monitors estimate contraction frequency and duration but not intensity, and signals are degraded by maternal body habitus and transducer malposition.

Montevideo units

Montevideo units sum the peak contraction amplitudes above resting tone over 10 minutes; values of 200 or more generally indicate adequate uterine activity.

Intermittent auscultation technique

A fetoscope or Doppler is used to count the fetal rate for 60 seconds after a contraction, with intervals determined by risk status and stage of labor.

Baseline rate determination

The baseline is the mean rate rounded to 5 beats per minute over a 10-minute window, requiring at least 2 minutes of interpretable tracing.

Moderate variability

Moderate variability is an amplitude of 6 to 25 beats per minute from the baseline and is considered the most reassuring finding on a fetal tracing.

Acceleration criteria

At 32 weeks or later, accelerations peak at least 15 beats per minute above baseline and last at least 15 seconds; earlier gestations use 10 by 10 criteria.

Early decelerations

Early decelerations are gradual, mirror contractions, and are mediated by vagal response to head compression; they are benign and require no intervention.

Variable decelerations

Variable decelerations are abrupt drops of at least 15 beats per minute lasting at least 15 seconds but under 2 minutes, reflecting umbilical cord compression.

Late decelerations

Late decelerations are gradual, begin after the contraction peak, and end after the contraction; they reflect uteroplacental insufficiency and require intervention.

Prolonged deceleration

A prolonged deceleration falls at least 15 beats per minute and lasts 2 to 10 minutes; a drop lasting 10 minutes or longer is a baseline change.

Sinusoidal pattern

A sinusoidal pattern is a smooth undulating baseline of 3 to 5 beats per minute at 3 to 5 cycles per minute lasting at least 20 minutes, suggesting fetal anemia.

Tachysystole definition

Tachysystole is more than 5 contractions in 10 minutes averaged over 30 minutes, classified as with or without fetal heart rate decelerations.

Resting uterine tone

Resting tone is the pressure between contractions; a baseline above 20 to 25 mm Hg suggests inadequate relaxation or intrauterine catheter malposition.

Contraction coupling

Coupling describes contractions occurring in pairs without adequate relaxation between them, which can reduce intervillous perfusion and impair fetal oxygenation.

Uterine hyperstimulation

Hyperstimulation is excessive contraction frequency, duration, or tone with nonreassuring fetal status; management includes stopping oxytocin and tocolysis per protocol.

Contraction intensity assessment

Palpation and external tocodynamometry cannot quantify intensity; only an intrauterine pressure catheter measures amplitude in millimeters of mercury.

Reactive nonstress test

A nonstress test is reactive with at least 2 accelerations meeting gestational-age criteria within 20 minutes, with up to 40 minutes allowed before calling it nonreactive.

Contraction stress test interpretation

A negative test shows no late decelerations with at least 3 contractions in 10 minutes; a positive test shows late decelerations with at least half of contractions.

Biophysical profile components

Five components scored 2 points each are fetal breathing, movement, tone, amniotic fluid volume, and nonstress test; 8 or 10 is generally reassuring.

Oligohydramnios thresholds

An amniotic fluid index of 5 cm or less or a maximum vertical pocket of 2 cm or less defines oligohydramnios, reflecting reduced fetal urine output.

Intrauterine resuscitation bundle

Measures include left lateral positioning, intravenous fluids, oxygen per protocol, stopping oxytocin, and vaginal examination to rule out cord prolapse.

Amnioinfusion indication

Amnioinfusion instills warmed saline through an intrauterine catheter to relieve recurrent variable decelerations from cord compression and to dilute thick meconium.

NICHD category III criteria

Category III includes absent variability with recurrent late or variable decelerations, bradycardia, or a sinusoidal pattern; these tracings require urgent evaluation and intervention.