Fetal Heart Monitoring

Question 1

Benefits of fetal heart rate monitoring (FHM)

Answer 1

Reassurance that the majority of the time, a good fetal/neonatal outcome is associated with normal continuous FHR data

Reduces expense that would be involved in 1:1 patient to nurse for intermittent auscultation

Provides warning of potential problems and gauges fetal response to actions undertaken to improve fetal conditions

Question 2

Drawbacks of fetal monitoring

Answer 2

Most studies reveal the incidence of neurologic damage and perinatal death with the use of electronic FHR monitoring is NOT significantly lower than that documented with older methods

Several studies have shown electronic FHR monitoring to increase operative vaginal deliveries and C sections

Non-reassuring continuous FHR monitoring may not be uniformly associated with poor perinatal outcome

Question 3

2 components to fetal monitoring strip

Answer 3

Upper tracing monitors FHR

Lower tracing measures uterine contractions

Question 4

Define normal uterine activity vs. tachysystole

Answer 4

Normal: 5 contractions or less in 10 minutes, averaged over a 30-minute window

Tachysystole: >5 contractions in 10 minutes, averaged over a 30 minute window; further characterized based on presence or absence of FHR decelerations

Question 5

What are montevideo units (MVU)?

Answer 5

Sum of contractions (uterine pressure readings from IUPC) in a 10 minute period

> 200 MVUs for at least 2 hours indicates contractions are strong enough

Question 6

Define baseline FHR

Answer 6

The mean FHR rounded to increments of 5 bpm during a 10 minute segment (assessed between contractions)

Normal = 110-160 bpm

Question 7

Causes of fetal bradycardia (<110 bpm)

Answer 7

Late sign of hypoxia

Obstetric anesthesia

Pitocin

Maternal hypotension

Prolapsed or prolonged compression of the umbilical cord

Heart block

Question 8

Causes of fetal tachycardia (>160 bpm)

Answer 8

Early sign of hypoxia

Medications - excessive oxytocin augmentation

Arrhythmias

Prematurity

Maternal fever

Fetal infection (chorioamnionitis is most common cause of fetal tachycardia)

Question 9

Baseline variability refers to fluctuations in the baseline FHR that are irregular in amplitude and frequency. It is usually quantified as the amplitude of peak-to-trough in bpm of change in baseline rate. What are the 4 designations used to describe degrees of baseline variability?

Answer 9

Absent = amplitude range undetected

Minimal = amplitude range detectable but <5 bpm

Moderate [NORMAL] = amplitude range 6-25 bpm

Marked = amplitude range > 25 bpm

Question 10

Decreased baseline variability is an indicator of possible fetal stress and its an ominous sign if associated with persistent late decelerations. It is also associated with hypoxia and acidemia. What are some causes of decreased baseline variability?

Answer 10

Prematurity, sleep cycle, maternal fever, fetal tachycardia, fetal congenital anomalies, maternal hyperthyroid, maternal drug use

Question 11

FHR may vary with uterine contractions by slowing or accelerating. How are these responses categorized?

Answer 11

1. No change
2. Acceleration
3. Deceleration (further categorized as early, variable, late, or prolonged)

Question 12

Define FHR acceleration

Answer 12

An abrupt increase in the FHR — a normal and reassuring response

> 32 weeks, an acceleration of >15 bpm above baseine for 15 seconds or more (but <2 minutes)

<32 weeks, acceleration of >10 bpm above baseline for 10 seconds or more (but <2 minutes)

Question 13

Define prolonged acceleration of FHR

Answer 13

Acceleration lasting >2 mins (considered a change in baseline if lasts >10 mins)

Question 14

Causes of FHR accelerations

Answer 14

Spontaneous fetal movement

Scalp stim or vibroacoustic stim

Vaginal exam

Question 15

Describe the cause of early decelerations, their appearance on FHR strip, and whether or not they are worrisome

Answer 15

Early decelerations occur secondary to head compression

Appear as “mirror image” to contractions

Not associated with fetal distress

Question 16

Describe the cause of variable decelerations and their appearance on FHR strip

Answer 16

Occur secondary to umbilical cord compression as abrupt decrease in FHR

Look like a sudden “V” shape on FHR strip (can occur before, during, or after contraction starts)

Decrease in FHR is >15 bpm lasting 15 seconds and <2 minutes in duration

Question 17

Describe the cause of late decelerations, their appearance on FHR strip, and whether or not they are worrisome

Answer 17

Caused by uterine placental insufficiency (UPI) [may be due to excess uterine activity, maternal supine hypotension, etc.]

Nadir of deceleration occurs after the peak of the contraction

Most ominous deceleration type — repetitive late decelerations usually indicate fetal metabolic acidosis and low arterial pH

Question 18

Define prolonged deceleration and when this is seen

Answer 18

Decrease in FHR from baseline that is >15 bmp lasting >2 mins but <10 mins

Commonly seen during maternal pushing

Question 19

Describe a sinusoidal pattern on FHR strip and what condition this is typically associated with

Answer 19

Smooth, sine wave-like undulating pattern in FHR baseline with a cycle frequency of 3-5/min

Seen with fetal anemia

Question 20

What 4 things must be reviewed and documented based on FHR strip?

Answer 20

Baseline FHR
Variability
Accelerations
Decelerations (specify type)

Question 21

A category I fetal heart rate tracing indicates a baseline of 110-160 bpm, moderate variability, no late or variable decelerations, and that accelerations and early decelerations may or may not be present. It is interpreted as a normal tracing. Thus the goal/management strategy is….

Answer 21

Intermittent or CEFM (continuous external fetal monitoring)

Question 22

A category II FHR tracing may indicate that there are recurrent variable decelerations (>50% of contractions, which may indicate umbilical cord compression with impending acidemia. What are the tx goals and management strategies in this case?

Answer 22

Goal is to alleviate cord compression

Tx options are to reposition mom, perform amnioinfusion (1st stage of labor), and modification of pushing efforts (push with every other contraction to allow baby to recover in between)

Question 23

Category II FHR also includes minimal or absent variability, recurrent late decelerations, prolonged decelerations, tachycardia, bradycardia, or variable/late/prolonged decelerations ocurring with maternal pushing efforts. The goals for management in these cases is to promote fetal oxygenation. What are some management strategies to do this?

Answer 23

Lateral positioning, IV fluid bolus, O2 administration, modification of pushing efforts, decrease in oxytocin rate, discontinuation of oxytocin/remove cervidil insert

Question 24

Tachysystole is considered category II FHR tracing, indicating possible spontaneous labor, or result of induction/augmentation. The goal in this cause is to reduce uterine activity, what are some management strategies to do this?

Answer 24

Lateral positioning, IV bolus, decrease oxytocin rate or discontinue, remove cervidil insert

If no response to the above, give uterine tocolytic agent (terbutaline)

Question 25

FHR is considered category III in the case of absent variability with recurrent late decels, recurrent variable decels, or bradycardia, as well as sinusoidal pattern. These tracings indicate increased risk of fetal acidemia and hypoxia. What is the next management step in these cases?

Answer 25

Prepare for delivery

Can try repositioning mom, IV bolus, O2 supplements, scalp stimulation test, but if there is no improvement with these then fetal delivery is advisable

Question 26

What is fetal scalp stimulationg and what is the purpose?

Answer 26

Scalp stimulation should cause acceleration of 15 bpm lasting 15 seconds, if this occurs the fetal pH value is almost always 7.22 or greater

This test is useful to differentiate fetal sleep from acidosis, when the fetal tracing shows reduced variability but no decelerations