Fetal surveillance Flashcards
Antepartum Testing & Monitoring
Antepartum Testing
Screening - noninvasive tests, maternal blood work, imaging
Diagnostic - invasive tests that involve obtaining a sample of material from inside the uterus containing fetal DNA
Chorionic Villus Sampling (CVS) between 10-13 weeks, and Amniocentesis between 15-20 weeks or later
Antepartum Monitoring = Fetal Monitoring when not in labor
Cardiotocography = Electronic fetal monitoring
Non-stress test (NST)
Contraction stress test (CST)
Biophysical Profile (BPP)
Maternal and fetal Indications for Antepartum Monitoring
Maternal Indications
Preterm labor, preterm prelabor rupture of membranes (PPROM)
Prior fetal demise
Pre-existing or gestational diabetes
Chronic or pregnancy-induced hypertension (gestational HTN or preeclampsia)
Rh Alloimmunization
Other pre-existing medical conditions - SLE, cyanotic heart disease, sickle cell anemia
Fetal Indications
Multiple gestations (twins, triplets, etc)
Post-dates pregnancy (40+ weeks)
Fetal growth restriction
Oligohydramnios
Decreased fetal movement (detected by mother)
What is Electronic Fetal Monitoring (EFM)?
Cardiotocography
Monitors fetal heart rate on one graph, and contractions (toco) on second graph over time
Provides data on how fetus is responding to intrauterine event
External monitoring: Doppler ultrasound on the maternal abdomen
Picks up artifact, movement. Difficult in abdominally obese patients. Need physical transducer on abdomen at all times.
Internal monitoring: Fetal scalp electrode
More invasive, need to feel fetal scalp transcervically in order to place.
Why use EFM?
For antenatal monitoring, EFM can give an idea of fetal well-being
During labor uterine contractions cause interruptions in fetal oxygenation, so EFM helps providers decide when to intervene (offer resuscitation or c-section, etc)
“Identification of FHR changes potentially associated with inadequate fetal oxygenation may enable timely intervention to reduce the likelihood of hypoxic injury or death.”
When to use EFM?
Upon admission to L&D, monitor patient 20-30 minutes
Monitor FHR at least every 30 minutes in first stage active labor
Monitor FHR at least every 15 minutes in the second stage
ACOG
Either continuous or intermittent monitoring acceptable for uncomplicated pregnancies.
Always continuously monitor high risk patients!
EFM Definitions
baseline
“The mean FHR rounded to increments of 5 beats per minute during a 10-minute segment.”
Count by increments of 5bpm
Minimum 2 minutes segment
Normal: 110 - 160bpm
Bradycardia: FHR < 110 bpm
Tachycardia: FHR > 160bpm
EFM definitions
Variability
“Fluctuations in the baseline that are irregular in amplitude and frequency.”
Resembles the variation from baseline, measured from highest to lowest FHR
Absent: No variation in baseline, undetectable
Minimal: < 5bpm
Moderate: 6-25bpm
Marked: >25bpm
Undetectable from baseline
ABSENT
< 5bpm variability of baseline
MINIMAL
6-25 bpm variability of baseline MODERATE
> 25bpm variability of baseline
MARKED
Ranges from 120 to 150 = marked
EFM defintiions
Accelerations
“A visually apparent abrupt increase (onset to peak less than 30 seconds) in the FHR”
Definition is based on gestational age
< 32 weeks: Increase in 10bpm in at least 10 seconds
>32 weeks: Increase in 15bpm in at least 15 seconds
Reassuring
Total acceleration should last less than 2 minutes!
Prolonged Accelerations / Decelerations
Accel or decel lasts >2 minutes
If a FHR pattern lasts more than 10 minutes, it is a change in baseline
Requires new interpretation
EFM definitions
Early Decelerations
Early
“Visually apparent usually symmetrical gradual decrease and return of the FHR associated with a uterine contraction.”
Gradual: Lasts >30 seconds from onset to nadir
Nadir of FHR align with contraction peak
Clinically benign (nonpathologic)→ head compression
No intervention needed
EFM defintions
Variable deceleration
“Visually apparent abrupt decrease in FHR.”
Onset to nadir < 30 seconds
Usually steep deceleration, >15bpm decrease in FHR
Umbilical cord compression
Resuscitation measures
Reposition patient to left-lateral side
Consider amnioinfusion (after membranes are ruptured, provider can place an intrauterine catheter that will infuse fluid back to the uterus and cushion the umbilical cord)
EFM definition
Late Decelerations
“Visually apparent usually symmetrical gradual decrease and return of the FHR associated with a uterine contraction.”
Gradual: Lasts >30 seconds from onset to nadir
Nadir of FHR begins after contraction peak
Cause - Hypoxemia and placental hypoperfusion
Always requires intervention
Physiology of Late Decelerations
Uterus contracts → compression of maternal uterine blood vessels → decreased placental perfusion
Decrease in delivery of oxygenated blood to placenta → decreased diffusion of oxygenated blood to fetus
Autonomic response triggers vasoconstriction and blood shunting → parasympathetic reflex to decrease HR & CO.
Potential causes of late decelerations and management
Post-epidural hypotension
Uterine tachysystole
Maternal hypoxia, vasculopathy
Placental disorders
Management:
Intrauterine resuscitation
Sinusoidal Pattern
“Visually apparent, smooth, sine wave-like undulating pattern in FHR baseline with a cycle frequency of 3-5 minute which persists for 20 min or more.”
Fetal anemia!!!!!
Classifications of Decelerations
Intermittent vs recurrent
Intermittent: Occur with less than half of the uterine contractions
Recurrent: Occur with more than half of the uterine contractions
Intrauterine Monitoring
Uterine activity normal and tachy
Normal uterine activity: 5 or less contractions in 10 minutes
Tachysystole: >5 contractions in 10 minutes
Also characterised by strength (mild/moderate/strong)
Non stress test (NST) - Antepartum Monitoring
Use the electronic fetal monitoring system for a minimum of 20 minutes to assess fetal well-being
Done outpatient in clinic/office, or in triage to discharge a patient home safely
Usually performed at viability ~24 weeks
Keep in mind the definition of accelerations and decelerations goes from 10bpm to 15bpm at 32weeks
Either REACTIVE or NON-REACTIVE
Reactive NST
Normal baseline 110-160bpm
Moderate variability
2 or more accelerations in 20 minute tracing strip
A reassuring pattern predicts a low likelihood of fetal demise due to hypoxic injury over next few days
Management - observation
Non-Reactive NST and management
Not achieving 2 or more accelerations in 20 minutes
Any decelerations
Any variability other than moderate
A non-reassuring pattern would indicate that provider is unable to rule out fetal demise due to hypoxic injury over next few days
Management
Further monitoring required
Normal baseline, moderate variability, no decelerations, but no accels = monitor for a few hours. Maybe baby was in a sleep cycle
Depending on gestational age & severity of non-reassuring NST, immediate delivery may be considered
Bradycardia with absent variability and full term = immediate cesarean delivery
Contraction Stress Test
Positive vs negative result
An NST where contractions are present (testing the fetus ability to withstand stress)
Either patient is spontaneously contracting, or a dose of pitocin is given to induce contractions
Negative CST
No significant decels
Reassuring result
Positive CST
Late decels >50% of the time
Non-reassuring result = intervene
Equivocal
Presence of late decels < 50% of the time, or inadequate contractions to assess
Biophysical Profile (BPP)
Non-invasive test to assess fetal well-being
Performed after 28 weeks
2 parts
NST (assessing the fetal heart rate)
Ultrasound to evaluate several things:
Fetal movement
Fetal tone
Fetal breathing
Amniotic fluid index
Scored out of 10 points, but each component is either 0 or 2 points
Fetal movement: 3+ discrete body or limb movements
Fetal tone: 1+ episode of fetal extremity (arm, hand, etc) flexing and extending
Fetal breathing: 1+ breathing episode lasting >30 seconds (can include hiccups)
Amniotic fluid volume: single deepest pocket >2x2cm
Amniotic fluid volume
Measuring the deepest vertical pocket in all 4 quadrants of the uterus
Here you can see the 4 quadrants all measured straight vertically
Added up for a total of 10.67
Normal is 5-25
EFM in Labor = Three Tiered Category System
❏Created to identify fetal distress
❏Helps determine if a fetal heart tracing is reassuring or non-reassuring
❏Normal, suspicious, or pathologic
Category 1
❏Healthy and reassuring
❏Can allow for intermittent monitoring
❏Low risk for development of fetal acidemia
❏No indications to change current intrapartum management
Category 3
❏Not reassuring
❏Increased risk of fetal hypoxic acidemia → can lead to cerebral palsy and neonatal encephalopathy
❏Scalp stimulation
❏+ acceleration (fetal acidosis unlikely)
❏No acceleration (50% acidosis)
❏DELIVER!!
❏Decision to delivery time < 30min
Category 2
What can affect a fetal heart tracing?
Maternal
❏Medications
❏Physiology
❏Comorbidities
Fetal
❏Cardiac arrhythmias
❏Neurologic injury
Fetal bradycardia/prolonged decelerations
❏Placenta abruption
❏Umbilical Cord Prolapse
❏Uterine Rupture
❏Tachysystole
Fetal Tachycardia
Causes:
❏Infection (presumed chorioamnionitis)
❏Medications (stimulants, beta-agonists)
❏Hyperthyroidism
❏Fetal tachyarrhythmia
❏Minimal variability without decelerations
Causes:
❏Fetal sleep cycle
❏CNS depressants (magnesium, opioids)
Additional Management and Interventions
Tocolysis
❏Attempt to relax uterus, stop contraction to restore fetal oxygenation
❏Terbutaline 0.25mg OR Nitroglycerin
❏Smooth muscle relaxant
Amnioinfusion
❏Infusion of saline through intrauterine pressure catheter
