Intrapartum FHR Monitoring Flashcards
What is the positive predictive value for fetal well being of a normal NST?
> 99%
What is the PPV of an abnormal tracing for hypoxia/acidosis?
< 50%
What is the definition of tachysystole?
> 5 UCs in 10 minutes
How is a baseline heartrate determined
Must be at least 2 minutes of baseline in a 10 minute period
What is the normal FHR baseline?
110 - 160
How many beats per minute does the fetal heart rate increase for a maternal temp?
Increase in 10 bpm for every 1 degree increase in maternal temp
In what setting is fetal tachycardia a sign of fetal hypoxia?
Only if the tachycardia is preceded by fetal deceleration (rebound tachycardia)
What are causes of fetal bradycardia?
Complete heart block associated with lupus antibodies, hypothermia, hypoglycemia
What is the definition of variability?
Fluctuations in FHR that are irregular in amplitude and frequency over a 10 minute window
What is the definition of moderate variability?
Change in amplitude of 6 - 25 bpm
What is the definition of minimal variability
Change in amplitude of 1-5 bpm
What is the definition of marked variability?
Change in amplitude of > 25 bpm
Does absent or minimal variability on it’s own predict fetal hypoxia or acidemia?
No, only in the setting of recurrent deceleration
What does Moderate variability reliably exclude?
Fetal metabolic acidemia
What is the definition of an acceleration in a fetus > 32 wga?
15 beat increase over baseline lasting 15 seconds but < 2 minutes
What is the definition of an acceleration in a fetus < 32 wga?
10 beat increase over baseline lasting 10 seconds but < 2 minutes
What is the definition of a prolonged acceleration?
> 2 minutes but < 10 minutes
FHR accelerations reliably exclude what in the fetus?
fetal metabolic acidemia
Accelerations guarantee a fetal pH greater than
7.2
Does absence of fetal accelerations reliably predict fetal acidemia?
No
What is the definition of recurrent decelerations?
Occurs with > 50 of uterine contractions in a 20 minute window
Late deceleration always indicate fetal _____ but NOT indicate fetal _____.
hypoxia, acidemia
What do the shoulders (slight increase in FHR at the beginning and end) of variable deceleration indicate?
Venous compression (decreased venous return) increases HR
How long does a true sinusoidal pattern last?
> 20 munutes?
What is a sinusoidal pattern associated with?
strongly associated with fetal hypoxia due to anemia
What is the definition of pathologic fetal acidemia?
pH of < 7.0 and a base deficit > 12 mEq/L
What is the percent risk of fetal seizures associated with pathologic fetal acidemia?
8%
What is the risk of death associated with pathologic fetal acidemia?
9%
What long term affect is a fetus at risk of with pathologic fetal acidemia?
increased risk for long term neurological complications
What percentage of fetuses will have no complications in the setting of pathologic fetal acidemia?
50%
What technique during labor can help determine if acidemia is present?
Scalp stimulation
What is the definition of a category 1 tracing?
normal baseline (110-160), moderate variability, No decelerations, +/- accelerations
What is the definition of a category 3 tracing?
Absent variability AND any of the following: recurrent late deceleration, recurrent variable decelerations, bradycardia, sinusoidal pattern
What is the definition of category 2 tracing?
ANYTHING ELSE: bradycardia but with variability, fetal tachycardia, absent/minimal variability BUT no decels, absent fetal accelerations, Decelerations but moderate variability,
External feta monitoring has ____ cesarean delivery rates and has ____ rates of CP
increased, had no affect on
FHR monitoring has a a ____ false negative rate but a ____ false positive rate
very low, very high
Both _____ and ____ reliably exclude metabolic acidemia
Moderate variability, fetal accelerations
