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OBGYN Clerkship > Fetal Monitoring > Flashcards

Fetal Monitoring Flashcards

1
Q

Normal fetal heart rate

A

110-160 bpm

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2
Q

Fetal HR acceleration

A

Increase of at least 15 bpm from baseline for at least 15 seconds

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3
Q

Categories of fetal heart rate

A

Category I: Normal baseline + variability. No late or variable deccelerations. Reassuring.

Category II: Indicates careful observation. (ex, fetal tachycardia w/o deccelerations)

Category III: Ominous. Increased likelihood of severe fetal hypoxia or acidosis. (ex, absent baseline variability with recurrent or late variable deccelerations or bradycardia)

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4
Q

Profound or prolonged fetal bradycardia is an indication for. . .

A

. . . immediate Cesarean section

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5
Q

“Early” vs “Late” vs “Variable” deccelerations

A

Early: Benign, thought to be caused by fetal head compression.

Late: Concerning, suggest fetal hypoxia or (if recurrent) acidemia. May be an indication for immediate Cesarean section

Variable: Concerning, suggesting cord compression. Abrupt and steep drop and an equally abrupt and steep resolution, and do not occur with every uterine contraction.

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6
Q

Baseline heart rate measurement

A
  • Approximate mean baseline rounded to units of 5 over a 10 minute period
  • Excludes periodic or episodic shifts from baseline
  • Represented as a single number, ie 145, 150, 155
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7
Q

Baseline heart rate by EGA

A
  • <32 weeks: High normal (around 150’s) is usually observed. During this time period the sympathetic nervous system is more developed than the parasympathetic system, and so sympathetic tone predominates.
  • 32 weeks and on: Heart rate gradually decreases in baseline due to rising vagal tone.
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8
Q

What to do when you aren’t sure if you’re hearing/seeing the maternal heart rate or the fetal heart rate

A

Palpate mom’s pulse or use an oximeter on mom’s finger

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9
Q

Degrees of variability

A
  • Absent: None
  • Minimal: <5 bpm variability
  • Moderate: 6-25 bpm variability
  • Marked: >25 bpm variability
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10
Q

What does fetal HR variability represent?

A
  • Reflects oxygenation and demonstrates an intact pathway between cerebral cortex, midbrain, vagus nerve, and heart
  • Moderate variability shows an intact CNS
  • When there is hypoxia, variability gradually decreases and eventually becomes absent
  • Important marker of fetal well-being
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11
Q

Potential etiologies of absent or minimal FHR variation

A
  • Poor oxygenation
  • Fetal sleep
  • Arrhythmia
  • Presence of certain anomalies
  • Medications or substances
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12
Q

FHR Accelerations

A
  • Visually abrupt increase in FHR above baseline
  • Onset to peak ~30 seconds
  • Definition: >15 bpm for >15 seconds
  • Usually lasts ~2 minutes
  • Measured during a non-stress test
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13
Q

FHR Accelerations in 28 - 32 week EGA

A
  • Definition: > 10 bpm for > 10 seconds
    • A bit more lenient than for >32 weeks
  • As such, standards of the non-stress test are different:
    • 2 accelerations within 20 minutes is reactive
    • Give 60 minutes (instead of 40) before calling non-reactive
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14
Q

FHR Accelerations in <28 weeks EGA

A

There usually are none! Often too early in development.

When FHM is used on these fetuses, it is primarily to check for normal baseline and check if it is appropriate for the EGA.

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15
Q

Prolonged acceleration

A

Change in FHR lasting between 2-10 minutes (2 min being the max cutoff for normal acceleration)

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16
Q

Baseline change

A

Change in FHR lasting between >10 minutes

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17
Q

Early deccelerations

A
  • Visually apparent GRADUAL decrease in fhr and return to baseline associated with contractions
  • Onset to nadir is > 30 seconds
  • Mirror image of contractions, uniform shape
  • Normal vagal response to intrauterine head compression
  • Completely benign
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18
Q

Mechanism of early deccelerations

A
  1. Fetal head is compressed within birth canal
  2. Intracranial pressure increases
  3. Cerebral blood flow changes
  4. Parasympathetic response
  5. Decreased fetal heart rate
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19
Q

Late decceleration

A
  • Visually apparent GRADUAL decrease of fhr and return to baseline associated with a contractions
  • Delayed in timing
  • Onset, nadir and recovery of decceleration occur after the onset, peak and end of contraction, respectively
    • (best to compare the onset of decceleration with peak of contraction)
  • Due to uteroplacental insufficiency
  • CONCERNING
20
Q

Mechanism of late deccelerations

A
  1. Decrease in uteroplacental oxygen supply to fetus
  2. Stimulates chemoreceptors
  3. Creates alpha adrenergic response, causing vasoconstriction
  4. Fetal hypertension
  5. Stimulates baroreceptors
  6. Parasympathetic response
  7. Decrease in FHR
21
Q

Persistent / continuous late deccelerations indicate. . .

A

. . . immediate delivery.

Mode of delivery depends on maternal status and on fetal status.

22
Q

First thing to ensure if late deccelerations are observed on FHM

A

Is the patient in supine position?

19% of patients in labor will demonstrate late deccelerations only in the supine position, due to supine hypotension syndrome.

23
Q

Variable deccelerations

A
  • Visually apparent ABRUPT decrease in fhr below baseline
  • Decrease is > 15 bpm lasting > 15 seconds
  • Lasts < 2 minutes
  • Caused by CORD COMPRESSION
24
Q

Mechanism of variable deccelerations

A
  • Compression of umbilical vein slows oxygen delivery to fetus
  • Decreases fetal blood pressure and oxygen saturation
  • Stimulation of baroreceptors and chemoreceptors
  • Increase in FHR and blood pressure
  • Umbilical artery is compressed, interupting flow to placenta
  • Baroreceptors triggered
  • Parasympathetic tone increases
  • Heart rate drops
  • Compression subsides, sympathetic response. . . . . .
    • It goes on and on. Variability depends on whether umbilical vein or artery is compressed at any given moment: Vein compression causes acceleration, artery compression causes decceleration.
25
Q

Etiologies of cord compression

A
  • Oligohydramnios
  • Maternal position
  • Fetal descent
  • Cord prolapse (vasa previa)
  • Cord entanglement / nuchal cord
  • Short or knotted cord
26
Q

Prolonged deccelerations

A
  • Visually apparent decrease in FHR below baseline
  • Decrease is > 15 min for 2-10 minutes
  • Several potential etiologies
27
Q

Etiologies of prolonged deccelerations

A
  • Prolapsed cord
  • Vaginal exam
  • Uterine hyperstimulation or hypertonus
  • Maternal hypotension (generalized or supine hypotension syndrome)
28
Q

Intrauterine resuscitation interventions

A
  • Blood pressure:
    • Reposition patient on L or R side (avoid supine hypotension syndrome)
    • Fluid bolus of 500 mL lactated ringers
    • 10 L oxygen on non-rebreather
    • If maternal hypotension after above, correct w/ ephedrine
  • Tocolysis:
    • Tell patient to stop pushing or only push with every third contraction
    • Stop oxytocin/pitocin, cervical ripening (pro-delivery interventions stopped)
    • Administer tocolytics (tertbutaline subcutaneously)
  • If after the above, variable deccelerations persist:
    • Amnioinfusion (effectively correcting oligohydramnios)
    • Vaginal exam
29
Q

Reasons for repositioning patient to L or R side or knee-chest during fetal distress

A
  1. Avoid supine hypotension syndrome
  2. Alters relationship between umbilical cord and uterine wall, avoiding cord compression
  3. May decrease frequency of contractions
30
Q

“Fetal reserve”

A

When maternal/placental/fetal system is functioning properly, the placenta provides the fetus with oxygen and nutrients above the basal needs – this is termed the fetal reserve.

Fetal reserve allows the fetus to withstand transient interruptions in blood flow and oxygenation that are common during labor

If there are problems w/ this system, fetus may be unable to withstand the stresses of labor

31
Q

Intensity range on uterine palpation

A
32
Q

Documentation of contractions

A
33
Q

If contractions on the monitor screen are opposite of what you feel on palpation, then you probably. . .

A

. . . put the probe too low on the abdomen.

34
Q

Calculating Mvus

A
35
Q

Normal resting uterine pressure during labor

A

~30 mmHg

36
Q

Definitions of tachysystole

A
  1. >5 contractions in 10 minutes
  2. Contractions lasting longer than 2 minutes
  3. Contractions occuring within 1 minute of one another
37
Q

Assessing FHR by auscultation

A
  • Rather than FHM, given as a baseline range
    • ex, Baseline is 130-140 bpm
  • Document rhythm
  • Should always be performed in context of assessment of uterine contractions
  • If any questions/suspicions, do FHM
38
Q

Category I EFM

A
  • NORMAL, strongly predictive of normal fetal acid-base status
  • Routine follow-up
39
Q

Category II EFM

A
  • INDETERMINATE, not predictive of acid-base status, yet no evidence to classify as I or III
  • Requires ongoing evaluation/surveillance and re-evaluation
  • Most common EFM pattern
40
Q

Category III EFM

A
  • ABNORMAL, predictive of acid-base status
  • Prompt eval to resolve with maternal oxygen, change in position, cessation of pitocin, treatment of maternal hypotension, IV bolus, treatment of tachysystole
41
Q

Sinusoidal EFM is a strong sign of. . .

A

. . . fetal anemia

42
Q

Key point regarding moderate FHR variability

A
  • Moderate variability reliably predicts the absence of metabolic acidemia at the time of observation
  • HOWEVER, the converse is not true. Minimal or absent FHR variation does not predict the presence of metabolic acidemia.
43
Q

Key point regarding accelerations in FHR

A
  • Presence of accelerations reliably predicts the absence of metabolic acidemia at the time of observation
  • HOWEVER, the converse is not true. Absence of accelerations does not predict the presence of metabolic acidemia.
44
Q

Sinusoidal EFM pattern indicates. . .

A

. . . fetal anemia or asphyxia

45
Q

Increased resistance in the placental circulation manifests as. . .

A

. . . increased Doppler blood flow in the umbilical arteries

46
Q

External tocodynamometry vs internal tocodynamometry

A

External: Tells you frequency of contractions

Internal: Tells you frequency and accurate intrauterine pressure readings of contractions.

Only internal may measure Montevideo units.

47
Q

___ variable decelerations are not concerning, but ___ variable decelerations are an indication for intervention.

A

Intermittent variable decelerations (occuring with less than 50% of contractions) are not concerning, but recurrent variable decelerations (occuring with more than 50% of contractions) are an indication for intervention.

OBGYN Clerkship (30 decks)

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