Fetal Assessment Flashcards
2 components of Antepartum fetal assessment
1) Maternal perception of fetal movement
2) Electronic Fetal HR monitoring (EFM) - CTG, NST, CST
Adequate Fetal kick count measurement after 28 weeks:
5 movements in 1 hour, 10 movements in 2 hours
Normal FHR
110-160 bpm
Causes of Fetal bradycardia (<110 bpm)
- Fetal congenital heart block/arrhythmias
- Fetal hypoxia
- Cord prolapse
- Epidural/spinal anesthesia
- Decrease in uterine blood flow (due to maternal HPN)
- Maternal hypothermia
Causes of Fetal tachycardia
- Maternal/fetal infection (most common)
- Chorioamnionitis
- 2nd stage of labor (activation)
- Maternal hyperthyroidism
- Drugs (betamimetics, methamphetamine, cocaine, tocolytic drugs, Parasympathetic drigs)
Single most important determinant of hypoxia or fetal acid base status
Variability
FHR Variability is a reflection of fetal _________ function
Autonomic system
Possible causes of decreased variability
- Hypoxia
- fetal sleep cycle (improves with VAS)
- Metabolic acidosis/acidemia (does not improve with VAS)
- congenital anomalies
- prematurity
Value of Normal variability (moderate variability)
5-25 bpm Variability
Value of Minimal variability
< 5 bpm Variability
Value of Marked variability
> 25 Variability
(consider acidemia)
Value of Absent variability
Undetectable variability
(consider cerebral hypoxia)
Definition of Fetal HR Acceleration (for < 32 weeks, and for > 32 weeks)
< 32 weeks:
Peak of ≥ 10 bpm above baseline for ≥10s but < 2 min
> 32 weeks
Peak of ≥ 15 bpm above baseline for ≥ 15s but < 2 min
Definition of Fetal HR Deceleration
Temporary decrease in FHR baseline < 110 for < 2 min.
Type of Fetal HR Deceleration:
Symmetrical gradual decrease and return of FHR to baseline associated with uterine contraction; WHEREIN the nadir of deceleration occurs after the peak of contraction
Late deceleration
Type of Fetal HR Deceleration:
Symmetrical gradual decrease and return of FHR to baseline associated with uterine contraction; WHEREIN the nadir of deceleration occurs at the same time as the peak of contraction
Early deceleration
Type of Fetal HR Deceleration:
Abrupt decrease in FHR ≥ 15 from baseline lasting ≥ 15s until < 2 min beginning at onset of uterine contraction; has a V or W shape
Variable deceleration
Type of Fetal HR Deceleration:
FHR deceleration ≥ 15 bpm from baseline lasting > 2 min
Prolonged deceleration
Usual cause of early decelerations
Fetal head compression (Common in Stage 2 of labor - dilatation to fetal delivery)
Usual cause/s of late deceleration
Uteroplacental insufficiency
- maternal hypotension
- placental dysfunction
Usual cause/s of variable deceleration
- Umbilical cord compression
- Oligohydramnios
- Placental insufficiency
Pathophysiology behind shouldering of V Waves in Variable deceleration
Uterine contraction > Umbilical vein compresses first > Slight increase in FHR > Umbilical artery compresses > Decrease in FHR > Umbilical artery decompresses first > Increase in FHR > Umbilical vein decompresses next > Normalization of HR to baseline
In a Non Stress test, FHR reactivity is measured by detecting ___________ in response to ____________
Fetal HR ; Fetal movement
Finding of a “Reactive NST”
≥ 2 accelerations in 20 minutes
*Acceleration: ≥15 increase in bpm above baseline for ≥ 15s but < 2 min
What is done after a Non-reactive NST to rule out fetal sleep cycles
Vibroacoustic stimulation.
Finding in a Non-reactive NST
< 2 accelerations in 40 mins
A Contraction stress test is a measure of uteroplacental insufficiency by detecting ____________ in response to ____________
Fetal HR decelerations; Uterine contractions
Finding of a Negative CST
No late or significant variable decelerations in an adequate strip (≤ 3 contractions in 10 min)
[NORMAL]
Finding of a Positive CST
Late decelerations following > 50% contractions (regardless of adequacy)
- indicates uteroplacental insufficiency
Finding of Equivocal-suspicious CST
Intermittent late or significant variable decelerations in < 50% of contractions
Finding of an Equivocal-hyperstimulatory CST
Decelerations in the presence of contractions every 2 min or lasting > 90s
Unsatisfactory
< 3 contractions in 10 min
Normal amount of uterine contractions
≤ 5 contractions in 10 minutes, averaged over 30 min
Finding of Tachysystole
> 5 contractions in 10 minutes
Values for mild, moderate, and strong contractions (mmHg)
Mild: < 40 mmHg
Mod: 40-70 mmHg
Strong: > 70 mmHg
Equation for Computing Montevideo units (to determine adequacy of uterine contractions)
Sum of uterine contraction amplitudes (above 20mmHg) within a 10 minute window
What other conditions are required for CS to be indicated in the setting of prolonged labor
- Adequate MVu
- ROM
- AOCD
- AOFD
Value for Normal Montevideo units (Adequate uterine contractions)
MVu ≥ 200mvu
What is the course of action for inadequate uterine contractions (MVu < 200u)
Give Oxytocin
CTG pattern seen in cases of fetal hypoxia from severe fetal anemia
Sinusoidal pattern (saw-tooth)
Other causes of Sinusoidal “saw-tooth” CTG pattern
- Severe fetal anemia
- fetal-maternal hemorrhage
- Twin-to-twin transfusion syndrome
- Rh alloimmunization
- Infection
- Cardiac malformation
- Hydrocephalus
- Gastroschisis
Immediate management of Late decelerations
- Left lateral decubitus (to relieve aortocaval compression
- Administer O2 via face mask
- Discontinue oxytocin
- Correct maternal hypotension
Immediate management of Variable decelerations decelerations
- Change to position of improved FHR pattern
- Administer O2 via face mask
- Discontinue oxytocin
- IE to check for cord prolapse or imminent delivery
- Consider amnioinfusion
FIGO consensus on intrapartum fetal monitoring:
Pathologic Variability values
> Decreased variability for > 50 min
Increased variability for > 30 min
Sinusoidal pattern for > 30 min
FIGO consensus on intrapartum fetal monitoring:
Pathologic Baseline values
FHR < 100bpm
FIGO consensus on intrapartum fetal monitoring:
Pathologic deceleration findings
> Repetitive late or prolonged decelerations in 30 mins
> Repetitive late or prolonged decelerations in 20 mins, if with min. variability
> Prolonged deceleration lasting > 5 min
Interpretation of EFM showing pathological signs (according to FIGO consensus)
Fetus with high probability of Hypoxia/acidosis
Side effect of MagSul administration seen on FHR monitoring
Reduced variability
This antenatal surveillance tool is used to evaluate placental blood flow in cases of intrauterine growth restriction
Umbilical doppler velocimetry ultrasound
The umbilical dopper velocimetry ultrasound assesses which vessel?
Umbilical artery
Umbilical artery flow velocity waveform in a normally growing fetus
High-velocity diastolic flow
Umbilical artery flow velocity waveform in a fetus with IUGR
Diminished diastolic flow
Umbilical artery flow velocity waveform in a fetus with extreme IUGR
Absent or reversed flow
5 variables of Biophysical profile
1) Amniotic fluid index
2) Fetal tone
3) Fetal movement
4) Fetal breath
5) Fetal HR acceleration (Reactive NST)
Definition of Reactive NST equivalent to a score of 2 on BPS
≥ 2 accelerations (≥ 15bpm for ≥ 15s) within 20 mins
Amniotic fluid volume equivalent to a score of 2 on BPS
Pocket of AFV measuring ≥ 2 cm in 2 perpendicular planes (2x2cm pocket)
Fetal tone findings equivalent to a score of 2 on BPS
≥ 1 episode of extremity extension with subsequent return to flexion
Fetal breath findings equivalent to a score of 2 on BPS
≥ 1 episode of rhythmic breathing lasting ≥ 30 sec within 30 mins
Fetal movement findings equivalent to a score of 2 on BPS
≥ 3 discrete body or limb movements within 40 mins
Cutoffs for BPS values and interpretation
Score 8-10 = Normal
Score 6 = Equivocal
Score < 4 = Abnormal
Which component of the BPS is the first to develop in the fetus and the last to go
Fetal tone
Component of the BPS that is optional if the other 4 are normal
Reactive NST
Component of the BPS that, if abnormal, requires further investigation even with a score of 8-10
Amniotic fluid volume < 2x2 cm pocket
Interpretation and course of action for a BPS score of 8 but with low or absent AFV
Interpretation: Suspected chronic fetal asphyxia
Action: Deliver
Interpretation and course of action for a BPS score of 6
Interpretation: Equivocal, Possible fetal asphyxia
Action:
Repeat BPS
Interpretation and course of action for a BPS score of 6, Repeat BPS is now < 6, and with abnormal AFV
Interpretation: Equivocal, Possible fetal asphyxia
Action:
Deliver
Interpretation and course of action for a BPS score of 6, Repeat BPS is the same, with normal AFV.
Patient is 35 weeks with unfavorable cervix
Interpretation: Equivocal, Possible fetal asphyxia
Action: Observe and repeat per protocol
Interpretation and course of action for a BPS score of 4
Interpretation: Probable fetal asphyxia
Action: Repeat test.
If still ≤ 4, Deliver.
Interpretation and course of action for a BPS score of 2
Interpretation: Almost certain fetal asphyxia
Action: Deliver.