Module 3 Assessment of Fetal Well Being During Labor and Birth

Question 1

Define FHR baseline

Answer 1

The baseline rate is the mean bpm (rounded to 0 or 5) over a 10-minute interval, excluding periodic changes, periods of marked variability, and segments that differ by more than 25 bpm. The baseline must be identifiable for two minutes during the interval (but not necessarily a contiguous two minutes); otherwise, it is considered indeterminate.

Question 2

What is a normal FHR baseline?

Answer 2

110 to 160 bpm

Question 3

What is FHR bradycardia?

Answer 3

below 110 bpm

Question 4

What is FHR tachycardia?

Answer 4

over 160 bpm

Question 5

Define FHR variability

Answer 5

Fluctuations in FHR baseline that are irregular in amplitude and frequency. Measured in a 10-minute window. The amplitude is measured from peak to trough. There is no distinction between short-term and long-term variability.

Question 6

What is absent FHR variability?

Answer 6

Absent = amplitude undetectable

Question 7

What is minimal FHR variability?

Answer 7

Minimal = amplitude 0 to 5 bpm

Question 8

What is moderate FHR variability?

Answer 8

Normal: Moderate = amplitude 6 to 25 bpm

Question 9

What is marked FHR variability?

Answer 9

Marked = amplitude over 25 bpm

Question 10

Define FHR acceleration

Answer 10

An abrupt* increase in the FHR. Before 32 weeks of gestation, accelerations should last ≥10 sec and peak ≥10 bpm above baseline. As of 32 weeks gestation, accelerations should last ≥15 sec and peak ≥15 bpm above baseline.

Note: Prolonged acceleration= ≥2 minutes but less than 10 minutes. An acceleration of 10 minutes or more is considered a change in baseline.

Question 11

Define an early FHR deceleration

Answer 11

A gradual* decrease and return to baseline of the FHR associated with a uterine contraction. The nadir of the FHR and the peak of the contraction occur at the same time. The deceleration’s onset, nadir, and termination are usually coincident with the onset, peak, and termination of the contraction.

Note: * “Gradual” and “abrupt” changes are defined as taking ≥30 seconds or <30 seconds, respectively, from the onset of the deceleration/acceleration to its nadir/peak.

Question 12

Define an late FHR deceleration

Answer 12

A gradual* decrease and return to baseline of the FHR associated with a uterine contraction. The deceleration is delayed in timing, with the nadir of the deceleration occurring after the peak of the contraction. The onset, nadir, and recovery usually occur after the onset, peak, and termination of a contraction.

Note: * “Gradual” and “abrupt” changes are defined as taking ≥30 seconds or <30 seconds, respectively, from the onset of the deceleration/acceleration to its nadir/peak.

Question 13

Define an variable FHR deceleration

Answer 13

An abrupt* decrease in FHR below the baseline. The decrease is ≥15 bpm, lasting ≥15 secs and <2 minutes from onset to return to baseline. The onset, depth, and duration of variable decelerations commonly vary with successive uterine contractions.

Note: * “Gradual” and “abrupt” changes are defined as taking ≥30 seconds or <30 seconds, respectively, from the onset of the deceleration/acceleration to its nadir/peak.

Question 14

Define an prolonged FHR deceleration

Answer 14

A decrease in FHR below the baseline of 15 bpm or more, lasting at least 2 minutes but <10 minutes from onset to return to baseline. A prolonged deceleration of 10 minutes or more is considered a change in baseline.

Question 15

What is the least invasive intrauterine resuscitation we can use?

Answer 15

Repositioning

Question 16

Should O2 be given as intrauterine resuscitation?

Answer 16

No-it is no longer recommended unless the maternal spo2 is <94%

Question 17

Why do we give IVF boluses for intrauterine resuscitation?

Answer 17

To maximize maternal intravascular volume:
-Improved cardiac output
-Increasing venous return
-Increasing left ventricular end-diastolic pressure
-Increasing ventricular preload
-Increased stroke volume

Question 18

What interventions can change uterine activity?

Answer 18

Stop/decrease pitocin
Reposition
IVF bolus
Tocolytic/Terbutaline

Question 19

Define tachysystole.

Answer 19

More than 5 contractions in a 10-minute period over 30 minutes

Question 20

What characteristics make a Category I tracing (EFM)?

Answer 20

Baseline: 110-160
Variability: Moderate
Accelerations: Present OR not present
Decelerations: NOT present

Question 21

What characteristics make a Category III tracing (EFM)?

Answer 21

Variability: Absent
with: recurrent variables or late decelerations
or: bradycardia

Pattern: Sinusoidal (Fetal anemia)

Question 22

What characteristics make a Category II tracing (EFM)?

Answer 22

Any tracing that is not category I or III

Question 23

What does a Category I tracing indicate?

Answer 23

Associate with normal acid-base balance, acute fetal acidemia absence 98-99% of the time:

Question 24

List fetal heart rate characteristics that can be assessed with intermittent auscultation.

Answer 24

Heart rate, rhythm, accelerations, and decelerations reliably

Cannot be used to differentiate between types of decelerations or determine baseline variability with accuracy

Question 25

Discuss the rationale for auscultating the fetal heart rate in between AND during contractions when using intermittent auscultation.

Answer 25

Auscultation between contractions helps to determine baseline FHR. Listening during a contraction helps to determine the presence or absence of accels and decels. Presence of episodic/periodic changes may warrant a change to EFM.

Question 26

When using IA, what characteristics make a Category I tracing?

Answer 26

-Normal FHR baseline between 110 and 160 bpm and,
-Regular rhythm and,
-Absence of FHR decreases or decelerations from the baseline

Note: Presence of FHR increases or accelerations from the baseline may or may not be present in a FHR auscultated and determined to be Category I. Accelerations should be assessed for and documented if present. If present, FHR accelerations signify fetal well-being at the time they are noted.

Question 27

When using IA, what characteristics make a Category II tracing?

Answer 27

-Irregular rhythm
-Presence of FHR decreases or decelerations from the baseline
-Tachycardia (baseline >160 bpm >10 minutes in duration)
-Bradycardia (baseline <110 bpm >10 minutes in duration)

I.e. anything that would not be category I IA is category II

Question 28

Discuss management of category II FHR changes when using intermittent auscultation

Answer 28

EFM should be used to verify or clarify an indeterminate or abnormal FHR pattern and guide management. Management of indeterminate FHR patterns depends on multiple factors, including whether the pattern is recurrent or resolves. Intrapartum resuscitation techniques such as position change, hydration, and correction of hypotension or hyperstimulation can be instituted as necessary. If the Category II FHR pattern does not resolve, transfer to EFM for further evaluation is recommended.

Question 29

Discuss the newer evidence on supplemental oxygen during labor for FHR abnormalities as reviewed in the ACOG Practice Advisory.

Answer 29

Until fairly recently, oxygen supplementation was an automatically accepted part of “intrauterine resuscitation” with category 2 or 3 EFM tracings. This has now changed. Based on this body of research, routine use of oxygen supplementation in individuals with normal oxygen saturation is not recommended for fetal intrauterine resuscitation.

Question 30

How do we resuscitate in utero?

Answer 30

-Reduction of contraction [D/C oxytocin]
-Position change/left lateral: to get off vena cava, may move off the umbilical cord.
-IVF hydration: dehydration can cause placental insufficiency
-O2 at 8-10 l/min: low 02=low 02 to baby. SPO2 of mom needs to be at least 94%
-Modify breathing and pushing techniques
-Amnioinfusion

Question 31

Compare continuous electronic fetal heart rate monitoring and intermittent auscultation in terms of rates of cerebral palsy, neonatal seizures, perinatal mortality, and cesarean births.

Answer 31

-A 2017 Cochrane review found no difference in APGAR, cord blood gases, rates of low O2 brain damage, admission to NICU, or perinatal death. This was consistent in low and high-risk pregnancies.
-There was a 50% lower seizure risk with EFM (1/500 births) 0.15% in EFM vs 0.3% in IA. There were no long term follow up studies.
-EFM had 63% higher chance of C/S and 15% more likely to have vacuum/forcep birth.
-There was no CP difference.
-No difference in stillbirth or newborn death rates

Question 32

How accurate is EFM at predicting CP risk?

Answer 32

Broken down: very poor at detecting (99.8% false positive)

In their 2009 practice bulletin, ACOG concludes that there is Level A evidence (based on good and consistent scientific evidence) that the false-positive rate of EFM for predicting cerebral palsy is greater than 99%. Put another way, most positive test results will be wrong. The false positive rate is so high that for every 1,000 fetuses with an abnormal heart rate pattern that indicates cerebral palsy is at risk of occurring, only one or two will go on to develop cerebral palsy (ACOG 2009).

Question 33

Understand the relationship between intrapartum asphyxia and neurological injury in the fetus.

Answer 33

Although intrauterine asphyxia is an established cause of neurologic damage, including cerebral palsy, determining the exact role of intrapartum asphyxia as a cause of permanent neurologic damage in a fetus is complicated. It is estimated that the overall incidence of neonatal encephalopathy attributable to intrapartum asphyxia alone (in the absence of antepartum abnormalities) is 1.6 per 10,000 births.

Question 34

What is asphyxia?

Answer 34

Progressive hypoxemia and hypercapnia with either metabolic or mixed (metabolic and respiratory) acidemia [Increased hydrogen ion concentration in blood]

Occurs when gas exchange is impaired enough to cause significant metabolic acidosis. As asphyxia progresses, the fetus loses the ability to protect vital organs.

Question 35

What are the recommendations for the frequency of fetal heart rate assessment during labor using EFM?

Answer 35

ACOG:
Low risk- q30m during the first stage, q15m during the second stage
High risk- q15m during the first stage, q5m during the second stage

Question 36

What are the recommendations for the frequency of fetal heart rate assessment during labor using IA?

Answer 36

ACOG- q15m during first stage, q5m during second stage
ACNM- q15-30m during active stage, q15m during second stage prior to pushing, q5m during pushing.
AWHONN- q15-30m during active phase of first stage, q5-15m during pushing phase of second stage.

Note: There are no absolute recommendations; rather, ranges are suggested

Question 37

How should you manage at Category I tracing?

Answer 37

Continue POC. No interventions required

Question 38

How should you manage at Category II tracing?

Answer 38

-Reduction of contraction [D/C oxytocin]
-Position change/left lateral: to get off vena cava, may move off the umbilical cord.
-IVF hydration: dehydration can cause placental insufficiency
-O2 at 8-10 l/min: low 02=low 02 to baby. SPO2 of mom needs to be at least 94%
-Modify breathing and pushing techniques
-Amnioinfusion [for variable only]

Question 39

How should you manage at Category III tracing?

Answer 39

Emergent delivery

Question 40

How does sympathetic and parasympathetic input affect FHR patterns?

Answer 40

Early in pregnancy, the FHR is higher than in later pregnancy due to the parasympathetic nervous system maturing in the second trimester. It then becomes dominant over the sympathetic and slows the baseline heart rate.

Variability is a result of the sympathetic and parasympathetic input (vagus stimulation causes successive beats to vary).

Question 41

How do chemoreceptors and baroreceptors affect FHR patterns?

Answer 41

Increased carbon dioxide causes chemoreceptors to signal the brain to slow the FHR. Baroreceptors detect changes in blood pressure. When BP rises, the FHR slows.

Question 42

What could FHR bradycardia indicate?

Answer 42

This could be due to rapid descent of the fetal head, idiopathic in post-term babies, opioid use, or maternal hypotension.

Acute: Uterine rupture, placental abruption, cord prolapse, shoulder dystocia, maternal hypotension, amniotic fluid embolism, vasa previa, and other causes.

Question 43

What could acute FHR tachycardia indicate?

Answer 43

Short periods of tachycardia are a normal response to transient hypoxemia. . Sustained tachycardia could indicate the development of acidemia, maternal or fetal fever/infection, cardiac arrhythmia, or idiopathic.

Could be a result of maternal medication

Question 44

What does an early deceleration indicate?

Answer 44

Head compression

Expected FHR variation in labor

Question 45

What does a late deceleration indicate?

Answer 45

These happen due to decreased fetal oxygen from decreased uteroplacental perfusion. Chemoreceptors detect hypoxemia and mediate a drop in the fetal heart rate “late” to contractions.

Recurrent lates occur due to uteroplacental insufficiency. This could be caused by DM, HTN, Hyperthyroidism, autoimmune disorders, placental abnormalities, and post-term. Can also occur due to hypotension, tachysystole, etc.

Late with variability represents a response to hypoxemia and does not indicate acidemia. Lates with minimal or absent variability is commonly associated with acidemia.

Question 46

What does a variable deceleration indicate?

Answer 46

Occurs due to an interruption in umbilical blood flow (aka cord compression)

Variables that return to baseline in 60 seconds with normal baseline and moderate variability are not associated with fetal acidemia. Variables with minimal or absent variability are associated with acidemia.

Question 47

What does a sinusoidal pattern indicate?

Answer 47

A sinusoidal pattern is characterized by an undulating, recurrent uniform fetal heart rate equally distributed 5 to 15 bpm above and below the baseline (Figure 26-10). The undulation occurs at a rate of 2 to 6 cycles per minute and is identified by an absence of short-term variability.

Cause: fetal acidemia (maternal-fetal hemorrhage, uterine rupture, placental abruption)

Question 48

What does the presence or absence of FHR variability signify?

Answer 48

The presence of moderate FHR variability signifies that the fetus has an intact cerebral cortex, midbrain, vagus nerve, and cardiac conduction system. Moderate variability is the single best indicator that the fetus does not have cerebral tissue hypoxia or ischemia. Approximately 98% of all fetuses with moderate variability will not have clinically significant acidemia at the time the variability is observed, even if recurrent fetal heart rate decelerations are present.

Question 49

What does minimal variability indicate?

Answer 49

Minimal variability without decels do not correlate with fetal acidemia. Could indicate fetal rest cycle (20-40 minutes but somtimes up to 80 minutes) or opiate/terb/pheneragn/medication use.

Question 50

What does absent variability indicate?

Answer 50

Absent without decels could be idiopathic and not consistently associated with fetal acidemia.

Question 51

What irregular FHR pattern is most associated with fetal acidemia?

Answer 51

Minimal or absent variability in the presence of recurrent late or variable decelerations