Fetal HR Monitoring and Antenatal Surveillance Flashcards
HISTORICAL FACTS MY FRIENDS
- Fetal heart first heard in 17th century by a physician in France named Marsac.
- Evory Kennedy published a book in 1833 in Dublin “Observations on Obstetric Auscultation.”
- The head stethoscope (fetoscope) was first reported in 1917 by David Hillis an Obstetrician in Chicago.
- The first commercially available monitor was produced by Hewlett-Packard in 1968.
What are the 2 external monitoring instruments?
- Tocodynamometer
2. Doppler
What are the 2 internal monitoring instruments?
- Intrauterine pressure catheter
2. Fetal scalp electrode
What does a tocodynamometer measure?
External contraction monitor…so it measures frequency and duration (NOT STRENGTH)
-This is the belt thing with the button on it
What does an intrauterine pressure catheter measure?
Strength, frequency, and duration
-This is inside the uterus
What does a doppler do?
US through abdomen that measures HR
What does a fetal scalp electrode measure?
It monitors the R-R of QRS complex and extrapolates HR…This is very accurate
What develops first, S or PS nervous system?
Sympatetic
What does the sympathetic nervous system give a base HR of?
150-160 bpm
-Remember, normal is 110-160 bpm
What does the development of the PS nervous system do?
Lowers the rate and gives variability…
Flat rates aren’t good… variability shows that the baby is neurologically intact
What is the PS nervous system mediated through?
The Vagus nerve
A normal FHR pattern indicates what?
Greater than 95% probability of well-being
True or False: FHR has a high false positive rate
TRUE- Good Apgar scores and normal pH in the presence of abnormal FHR patterns is 80%
So what kind of tool is FHR monitoring?
Screening (not diagnostic)
What is a normal fetal heart rate?
110-160 bpm
What constitutes tachycardia in a fetus?
Over 160 bpm
What constitutes bradycardia in a fetus?
Under 110 bpm
What are baseline characteristics with FHR monitoring?
FHR and variability
What are periodic and episodic changes seen with FHR monitoring?
Accelerations and decelerations
What are causes of tachycardia?
- MATERNAL FEVER
- INFECTION- maternal or fetal
- Hypoxemia
- Prematurity
- Dehydration
- Thyrotoxicosis
- Pharmacological Agents
What are causes of bradycardia?
- HYPOXEMIA
- Pharmacological Agents
- Fetal Arrhythmia’s (heart block)
- Maternal Hypotension.
What changes over time of the fetal heart rate?
Variability
True or False: The more variability the better
TRUE.. More variability, baby is well
What are 2 types of variability?
Short term and long term
What is short term variability?
Beat to beat changes in FHR
What is normal short term variability?
Between 5-25 bpm
What is long term variability?
Undulations of fetal HR around baseline
How many undulations per minute is normal?
3-5
True or Fase: A good baby will have an increase over baseline of 15bpm lasting at least 15 seconds
TRUE- This ensures the absence of fetal acidosis
Changes in baseline FHR can be related to what?
Uterine contractions
What are 2 types of changes in baseline FHR related to uterine contractions?
- Accelerations
2. Decelerations
What are accelerations?
FHR increase in response to uterine contractions
What are decelerations?
FHR decreases in response to uterine contractions
-Decelerations can be early, late, variable, or mixed
Describe early decelerations
Has an onset, maximum fall and recovery that coincides with the onset, peak and end of the uterine contraction
What do early decelerations result from?
Fetal head compression (Vagal response)
Are early decelerations gradual?
Yes… onset to nadir >/= 30 seconds decrease in with return to baseline
-This coincides with the peak of contraction like a mirror image
Are early decelerations associated with fetal distress?
No
Describe late decelerations
Onset, e maximal decrease and recovery that is shifted to the right in relation to the contraction
What are late decelerations associated with?
Uteroplacental insufficiency
WHat is more pronounced with severe decelerations?
Fetal hypoxia and acidosis
What are late decelerations associated with?
Low scalp pH values and high base deficits (indicating metabolic acidosis)
What is the severity of a late deceleration graded by?
The magnitude of the decrease in FHR at the nadir
What is most frequently encountered abnormal FHR pattern?
Variable decelerations
What causes variable decelerations?
Umbilical cord compression
Describe variable decelerations
Variable time of onset, variable form and may be nonrepetitive
If cord compression is prolonged, what can happen?
Hypoxia can be present and show a combined respiratory and metabolic acidosis
Hos is severity of a variable deceleration graded?
By their duration
More detailed description of variable deceleration?
-Visually Apparent, abrupt (onset to nadir or = to 5bpm below the baseline and lasts > or = 15 sec but < 2 minutes.
What is a prolonged variable deceleration?
> or = to 15bpm below baseline lasting > or = to 2min but < 10 min
What are 5 strategies for intervention in variable decelerations?
- STOP PITOCIN !!!!!!
- Change in maternal position left to right.
- 100% O2.
- Amnioinfusion
- Delivery
What are 6 strategies for intervention in late decelerations?
- STOP PITOCIN !!!!!!
- Change in maternal position left to right. Supine Hypotension (Poseiro Effect)
- 100% O2.
- Scalp Stimulation: Rub head with finger
- Tocolytics
- Delivery- if fetus is in distress and vaginal delivery is remote, Cesarean Section is indicated.
What is the passage of fecal stool into the amniotic fluid?
Meconium
When does early passage of fetal stool into the amniotic fluid occur?
Prior to rupture
When does late passage of fetal stool into the amniotic fluid occur?
After rupture, is usually heavy and caused by cord compression, stress, ect.
What is associated with poorer outcome related to meconium?
Heavy meconium…? huh
What is the treatment for passage of fetal stool into the amniotic fluid?
Amnioinfusion
What is indicated when fetal distress is suggested?
Fetal Scalp pH
Fetal blood pH correctly predicts neonatal outcome what % of the time?
82%
What is the false positive and false negative rate with fetal scalp pH?
- False +: 8%
- Flase -: 10%
A pH less than what indicates what the fetus is distressed?
7.25
Cerebral dysfunction doesn’t seem to occur unless what 3 things happen?
- 5 minute apgar score is less than 3
- Umbilical artery blood pH is less than 7
- Resuscitation is necessary at birth
What has happened to the frequency of cerebral palsy?
The frequency of it is unchanged (2/1000)
What are 2 reasons to use antenatal surveillance?
- To indentify patients at risk of fetal mortality or morbidity
- To decrease the mortality and morbidity rate
What are some patients at risk that should have antenatal surveillance?
- Post date pregnancy
- HTN
- Diabetes
- Previous stillborn
- IUGR
- Renal Disease
- Multiple Gestation
- Other: Hyperthyroidism, anemia, ect.
What counts as post-date pregnancy?
After 42 weeks
-Really, death goes up after 41.5, but anything after 41 is higher risk
What does a non stress test measure?
Baseline FHR, accelerations, and variability
What is a reactive non stress test?
2 accelerations of 15bpm above baseline lasting 15 seconds each in a 20 minute period
What is a non-reactive non stress test?
One of the things in a reactive stress test is lacking
-Like 1 acceleration, it doesn’t go 15bpm above baseline, or there are no accelerations
When is a non stress test usually done?
After 32 weeks gestation
What is a good outcome for a non stress test?
REACTIVE
What are 2 other names for a contraction stress test?
Oxytocin stress test or nipple stim test
What is required for a contraction stress test?
Must have 3 contractions lasting 40-60 seconds in a 10 minute period
What does the contraction stress test approximate?
The stress a fetus might have in the 1st stage of labor
When is a contraction stress test usually done?
When there is no danger of preterm labor, uterine rupture, ect.
Would you do a contraction stress test preterm?
NOOOOOOO… what if you can’t stop the labor… baby needs to be at least 37 weeks
So what is the general idea with a contraction stress test?
To cause contractions to see how the baby would respond
What is a negative CST test?
No late decelerations with adequate contraction
What is a positive CST test?
Late decelerations with >50% of the contractions
-So basically late decelrations after 2 contractions
What is a suspicious CST test?
Inconsistent late decelerations under 50%
-So maybe a late deceleration after 1 contraction
What is an unsatisfactory CST test?
Inadequate uterine activity- No contractions induced
What does a biophysical profile use?
Real time US and an NST
What are 5 components measured by a BPP?
NST, fetal breathing movement, fetal tone, fetal movement, and amniotic fluid volume
What is the max score on a BPP?
- .. get a score of 2 or 0 for each category
- AKA you can’t get an odd number for a score with this test
How is fetal breathing assessed?
Movement of the diaphragm
What 3 tests can be done to determine fetal well being?
NST, CST, BPP
What gets 2 points for fetal breathing movement?
At least one episode of >30 seconds in a 30 minute period
- Diaphragm moving
- This takes time so a tech has to do it
What gets 2 points for gross body movement?
3 discreet body, limb movements in a 30 minute period
What gets 2 points for fetal tone?
One episode of active expansion with return to flexion of fetal limbs, hands, or trunk
-Basically just stretching or even moving limbs
What gets 2 points for NST?
Reactive test
What gets 2 points for amniotic fluid volume?
At least 1 pocket of amniotic fluid volume measuring 2cm in 2 perpendicular planes
- If there is low fluid… probably intervene
- Assess the 4 quadrants of the uterus
What is done with a BPP score of 10?
Normal… repeat weekly
What is done with a BPP score of 8?
Normal…repeat weekly or twice weekly in diabetics or post-dates
-If there is oligohydraminos, DELIVER
What is done with a BPP score of 6?
Suspect chronic asphyxia
-Greater than 36 weeks, DELIVER
What is done with a BPP score of 4?
Suspect chronic asphyxia
-If greater or equal to 32 weeks, DELIVER
What is done with a BPP score of 0-2?
Strongly suspect asphyxia
-DELIVER REGARDLESS OF AGE
What is the most and least important past of a BPP?
- Most important is fluid
- Least important is breathing (“last to go, first to show”)
When would you test a pregnant lady with diabetes?
28-40 weeks (depends on type)
When would you test a pregnant lady with preeclampsia?
At diagnosis >26 weeks
When would you test a post-date pregnant lady?
41-42 weeks
When would you test a IUGR lady?
At diagnosis
When would you test a lady with a previous stillbirth?
32 weeks
When you are using an intrauterine monitor for HR, where should it be?
On the hard part of the scalp… no the fontanelle
-This will measure HR and contraction
In monitoring a baseline rate, the mean FHR is rounded to increments of 5BPM during a 10 minute segment excluding?
- Period or episodic changes
- Periods of marked FHR variability
- Segment of the baseline that differ by more than 25bpm
True or False: In any 10 minute window, the minimum baseline duration must be at least 2 minutes or the baseline is considered indeterminate
TRUE
What is the definition of variability?
Fluctuations in baseline FHR of 2 cycles per minute or greater, irregular in amplitude, and frequency, and visually quantitated as the amplitude of peak to trough
What is absent baseline variability?
Amplitude range is undetectable
What is minimal baseline variability?
Amplitude range 2-5 bpm
What is moderate baseline variability?
Amplitude range 6-25 bpm
What is marked-amplitude variability?
Over 25 bpm
What kind of monitors do most patients get?
External
-Really only internal if patient is already in labor and you need to keep an eye on the baby
What acceleration indicates fetal well being (not hypoxic)?
15 seconds, 15 beats above the baseline
- 2 of these in a 20 minute period
- This is the reactive NST
What do decelerations indicate?
Change in fetal oxygenation for different reasons
Is minimal variability good?
NO
What is an early deceleration due to?
Transient vagal response… head is compressed into pelvis… this isn’t a bad thing… seen in full-blown labor
Where do early decelerations happen?
Right over the contraction
What do variable decelerations look like?
A V… they are variable when they occur and are the most common and most frequent decelerations
What causes variable decelerations?
Cord compression
When do late decelerations happen?
They lag behind the contraction…this is bad
What are late decelerations due to?
Uteral-planceta deficiency… the baby isn’t recovering from the contractions and this is BAD
If there are repetitive late decelerations…50% or more what can you do?
SOMETHING
-O2, shift position (Left-lateral recumbent), prep C-section, internal monitors
What is an acceleration?
Visually apparent abrupt increase in FHR above the baseline with onset to peak in under 30 seconds
-Duration is quantitated from beginning to end of acceleration
Accelerations beyond 32 weeks?
15 bpm above baseline… duration is 15 seconds to 2 minutes
Accelerations prior to 32 weeks?
10b bpm above baseline… duration is 10 seconds to 2 minutes
What is the duration of a prolonged acceleration?
2- 10 minutes
What is considered a bseline change?
Acceleration of more than 10 minutes
