Varney's Ch 27 Fetal Ax During Labor

Question 1

What are the five components necessary for optimal maternal–fetal gas exchange?

Answer 1

• Adequate flow of well-oxygenated maternal blood into the intervillous space
• A large enough placental area for gas exchange
• Efficient diffusion of gases across the placental tissues
• Unimpaired umbilical vein circulation into the fetus
• Adequate oxygen transport capacity in the fetus

Question 2

What is the estimated blood flow to the uterus at the beginning of pregnancy?

Answer 2

20 to 50 mL per minute

Question 3

What is the approximate blood flow to the uterus at term?

Answer 3

500 to 900 mL of maternal blood

Question 4

What role does the umbilical vein play in fetal circulation?

Answer 4

It provides unimpaired circulation of oxygenated blood into the fetus

Question 6

What is the definition of Baseline rate?

Answer 6

Mean FHR rounded to increments of 5 bpm during a 10-minute segment excluding periodic or episodic changes, periods of marked variability, and segments of baseline that differ by > 25 bpm. Duration must be ≥ 2 minutes.

Baseline FHR is a key measure in fetal heart monitoring.

Question 7

What is the Baseline rate for Bradycardia?

Answer 7

Baseline rate < 110 bpm.

Bradycardia indicates a slower than normal fetal heart rate.

Question 8

What is the Baseline rate for Tachycardia?

Answer 8

Baseline rate > 160 bpm.

Tachycardia indicates a faster than normal fetal heart rate.

Question 9

Define Variability in fetal heart rate monitoring.

Answer 9

Fluctuations in the baseline FHR ≥ 2 cycles/min.

Variability is an important indicator of fetal well-being.

Question 10

What is meant by Absent variability?

Answer 10

Amplitude from peak to trough undetectable.

Absent variability may indicate potential fetal distress.

Question 11

What characterizes Minimal variability?

Answer 11

Amplitude from peak to trough > undetectable and ≤ 5 bpm.

Minimal variability can suggest some level of fetal compromise.

Question 12

What is Moderate variability?

Answer 12

Amplitude from peak to trough 6–25 bpm.

Moderate variability is generally considered a reassuring sign.

Question 13

What defines Marked variability?

Answer 13

Amplitude from peak to trough > 25 bpm.

Marked variability may require further evaluation.

Question 14

What is an Acceleration in fetal heart rate?

Answer 14

Visually apparent abrupt increase (onset to peak < 30 seconds) of FHR above baseline. Peak ≥ 15 bpm. Duration ≥ 15 bpm and < 2 minutes.

Accelerations are often associated with fetal movement and are a positive sign.

Question 15

Define Prolonged acceleration.

Answer 15

Acceleration ≥ 2 minutes and < 10 minutes.

Prolonged accelerations may indicate a response to stimuli or other factors.

Question 17

What is early deceleration in fetal heart rate (FHR) monitoring?

Answer 17

Visually apparent gradual decrease of FHR below baseline with a return to baseline associated with a uterine contraction.

Onset of deceleration to nadir is ≥ 30 seconds, and the onset, nadir, and recovery occur simultaneously with the contraction.

Question 18

How does late deceleration differ from early deceleration?

Answer 18

Visually apparent gradual decrease of FHR below baseline with a return to baseline associated with a uterine contraction, but the nadir occurs after the peak of the contraction.

Onset of deceleration to nadir is ≥ 30 seconds, and the onset, nadir, and recovery occur after the contraction.

Question 19

Define variable deceleration in FHR monitoring.

Answer 19

Visually apparent abrupt decrease in FHR below baseline with a decrease ≥ 15 bpm below baseline and a duration of ≥ 15 seconds and < 2 minutes.

Onset of deceleration to nadir is < 30 seconds.

Question 20

What characterizes prolonged deceleration?

Answer 20

Visually apparent decrease in FHR below baseline with a decrease ≥ 15 bpm below baseline and a duration of ≥ 2 minutes but < 10 minutes.

This includes the time from onset to return to baseline.

Question 21

In early deceleration, when does the return to baseline occur?

Answer 21

Return to baseline occurs associated with a uterine contraction.

The timing aligns with the contraction’s onset, peak, and recovery.

Question 22

In late deceleration, when does the nadir occur in relation to the contraction?

Answer 22

The nadir occurs after the peak of the contraction.

This timing is crucial for distinguishing late deceleration from early deceleration.

Question 23

True or False: Variable deceleration has a gradual decrease in FHR.

Answer 23

False

Variable deceleration is characterized by an abrupt decrease in FHR.

Question 24

Fill in the blank: In prolonged deceleration, the duration is _______ minutes but less than 10 minutes.

Answer 24

≥ 2

This defines the time from onset to return to baseline.

Question 25

What are the three most common reasons for fetal hypoxia?

Answer 25

1) low oxygen in maternal blood 2) insufficient uterine/placental blood flow 3) insufficient umbilical blood flow

Question 26

How can an abnormal contraction pattern cause fetal hypoxia?

Answer 26

Too many ctxns do not allow enough oxygen perfusion time in-between. (5 or more ctxns in 10 mins lowers FSpO2 by 20% in 30 mins)

Question 27

What is a concerning cause of a transient decrease in heart rate for a fetus during labor?

Answer 27

fetal hypoxia

Question 28

Which cranial nerve controls the fetal heart rate via parasympathetic pathway? When stimulated, does the heart rate go up or down?

Answer 28

10th cranial nerve (vagus nerve). When stimulated the heart rate goes down.

Question 29

What is the cause of in-utero respiratory acidosis?

Answer 29

compromised maternal-fetal gas exchange between placenta and fetus, where the CO2 cannot be eliminated properly and builds up in the fetus.

Question 30

1) What does HIE stand for? and 2) What is the newest term to use now?

Answer 30

1) HIE=hypoxic-ischemic encephalopathy 2) Now use "neonatal encephalopathy" (NE)

Question 31

What is the term for multi-organ dysfunction of the fetus after 35 weeks?

Answer 31

neonatal encephalopathy (NE)

Question 32

What is therapeutic hypothermia a treatment for?

Answer 32

neonatal encephalopathy

Question 33

What is the criteria for therapeutic hypothermia?

Answer 33

>36 weeks who have the following within 1 hr of birth, hx of acute perinatal event, and Apgar ≤ 5 at 10 mins or 10 mins of PPV 1) cord pH ≤ 7.0 -OR- base deficit ≥ -16 -OR- 2) cord pH 7.01-7.15 -OR- base deficit of -10 to -15

Question 34

Continuous fetal monitoring showed an increase of cesarean sections by what percent when compared to intermittent fetal monitoring?

Answer 34

50% increase

Question 35

What conditions are associated with fetal tachycardia?

Answer 35

1) fetal hypoxia also evidenced by late decels, recurrent variables, decreased variability 2) infection - maternal or fetal 3) fetal anemia 4) placental abruption 5) maternal hyperthyroidism

Question 36

What are non-hypoxic causes of fetal bradycardia?

Answer 36

1) postmature fetus 2) rapid descent (head compression) 3) maternal anesthesia (epidural)

Question 37

What are hypoxic causes of fetal bradycardia?

Answer 37

1) prolapsed cord 2) placental abruption 3) uterine rupture 4) vasa previa

Question 38

At what fetal heart rate are coronary and cerebral oxygenation preserved?

Answer 38

80 bpm with variability

Question 39

What fetal heart rate is an emergency?

Answer 39

60 bpm

Question 40

What is the best indicator of fetal health and oxygenation?

Answer 40

FHR variability. This signifies that the fetus has an intact cerebral cortex, midbrain, vagus nerve, and cardiac conduction system.

Question 41

Which type of deceleration "mirrors the contractions"?

Answer 41

Early decelerations. The onset, nadir, and resolution coincide with the contraction.

Question 42

What type of decelerations are caused by decreased uteroplacental perfusion?

Answer 42

late decelerations

Question 43

How do late decelerations align with the contractions? before, during, or after?

Answer 43

They start after the peak of the contraction.

Question 44

What are maternal causes of chronic uteroplacental insufficiency from narrow spiral arteries, small placentas, and/or infarcts?

Answer 44

1) maternal HTN 2) diabetes 3) hyperthyroidism 4) autoimmune d/o 5) uterine tachysystole

Question 45

What is a fetal causes of uteroplacental insufficiency?

Answer 45

anemia

Question 46

What are common causes of variable decelerations?

Answer 46

1) cord compression 2) head compression during pushing

Question 47

What does a sinusoidal pattern look like?

Answer 47

An undulating recurrent uniform FHR equally distributed 5-15 bpm above and below the baseline 2-6 cycles per min.

Question 48

What Category is a FHR of 120 bpm with moderate variability and an absence of late or variable decelerations?

Answer 48

Category 1

Question 49

What is the Category of a FHR with a HR of 120 bpm and minimal variability and no accelerations.

Answer 49

Category 2

Question 50

What is the Category of a FHR of 165 bpm with moderate variability and accelerations?

Answer 50

Category 2

Question 51

What is the Category of a FHR of 140 bpm with absent variability and recurrent late decelerations?

Answer 51

Category 3

Question 52

What intervention can be used to evaluate if a fetus has a pH of 7.2 or higher?

Answer 52

FSS (fetal scalp stimulation) or VAS (vibroacoustic stimulation) performed between contractions. -must elicit a FHR acceleration of 15 bpm lasting at least 15 seconds.

Question 53

What interventions can be tried to improve fetal oxygenation?

Answer 53

1) position change (side-lying) 2) IV fluid bolus 3) O2 4) tocolytics (slow/stop ctxns)

Question 54

When would you consider having the mother push with every other contraction, instead of with each contraction?

Answer 54

To improve fetal oxygenation and improve FHR tracings (severity or frequency of decelerations)

Question 55

What is amnioinfusion used for?

Answer 55

Improvement in FHR when there is recurrent cord compression, recurrent variable decels or prolonged decels.

Question 56

How does a bolus of IV fluids for the mother effect contractions and fetal oxygenation?

Answer 56

1) Can reduce the frequency of ctxns by diluting oxytocin concentrations. 2) Increase fetal O2 by optimizing placental perfusion

Question 57

Is there clear evidence that maternal O2 improves the fetal oxygenation?

Answer 57

No

Question 58

How does a preterm fetus differ on FHR tracings?

Answer 58

1) Higher baseline FHR 2) smaller acceleration amplitude 3) decreased variability 4) frequent short/shallow variable decels

Question 60

What FHR pattern would you expect to see with infection?

Answer 60

Tachycardia