Fetal Heart Monitoring Flashcards
types of monitoring
External
-continuous
-if uncomplicated- q 30 min in active phase of 1st stage; q 15 min in second stage of labor
-if complicated- q 15 min in active phase of 1st stage; q 5 min in second stage of labor
Internal- most accurate tracings
external electronic fetal monitoring
- doppler US- fetal heart
- pressure sensitive tocodynamometer- detects/records contraction- measures freq of contractions
internal electronic fetal monitoring
- FSE (fetal scalp electrode)- monitors heart
- IUPC (intrauterine pressure catheter- intensity of contractions
- Requires membranes to be ruptured
hypoxia and fetal heart rate changes
- fetal oxygen reserve- enough for 1-2 min
- during contraction, blood flow from maternal circulation is interrupted
- fetal HR- atrial pacemaker
- a fetus whose oxygen supply is marginal cannot tolerate the stress of contractions- becomes hypoxic- can cause anaerobic metabolism- pH <7.20 is abnormal
fetal monitoring strip
- upper tracing- monitors FHR
- lower tracing- monitors uterine contractions
uterine activity- normal, tachysystole
- normal- 5 contractions or less in 10 min (avg over 30 min window)
- tachysystole- >5 contractions in 10 min (presence or absence of assoc FSH decelerations)
FHR- definitions
- baseline- normal, tachycardia, bradycardia
- baseline variability- absent, minimal, moderate and marked
- accelerations
- decelerations- early, variable, late, prolonged
- sinusoidal pattern
FHR- baseline
- normal- 110-160 bpm
- tachycardia- > 160
- bradycardia- <110
causes of bradycardia
- fetal hypoxia- late sign
- obstetric anesthesia
- pitocin
- maternal hypotension
- prolapsed or prolonged compression of umbilical cord
- heart block
causes of tachycardia
- fetal hypoxia- early sign
- medications- excessive oxytocin
- arrhythmias
- prematurity
- maternal fever
- fetal infection- chorioamnionitis- most common cause of tachycardia!!!
FHR baseline variability
fluctuations in baseline FHR that are irregular in amplitude and frequency
- absent- amplitude range undetected
- minimal- amplitude range detectable but < 5 bpm
- moderate- amplitude range 6-25 bpm
- marked- range > 25
Decreased variability
- indicator of possible fetal stress
- is ominous if assoc with persistent late decelerations
- assoc with hypoxia and acidemia
causes of dec baseline variability
- prematurity
- sleep cycle
- maternal fever
- fetal tachycardia- chorioamnionitis
- fetal congenital anomalies
- maternal hyperthyroidism
- maternal drugs/substances
Periodic FHR changes
- no change
- acceleration
- deceleration- early, variable, late, prolonged
aceleration
- normal reassuring response!!
- > 32 wks- HR of > 15 bpm above baseline for 15 s or more (<2 min)
- <32 wks- HR > 10 bpm for 10 s or more (<2 min)
prolonged acceleration
- > 2min
- change in baseline if acceleration lasts > 10 min
causes of accelerations
- spontaneous fetal movement
- scalp stimulation or vibroacoustic stim
- vaginal examination
Decelerations
- early
- variable
- late
early deceleratoins
-secondary to head compression
-not assoc with fetal distress
-occurs at the same time of the peak of the contraction- “mirror image”
(dec cerebral blood flow- act vagus n- dec HR)
variable decelerations
- secondary to umbilical compression
- abrupt dec in FHR
- dec in FHR is >15 bpm lasting > 15 sec (< 2 min)
late decelerations
- caused by UPI (uterine placental insuff)
- most ominous deceleration- repetitive late decelerations indicate fetal metabolic acidosis
- occurs after the peak of contraction
late decelerations- potential causes
- excessive uterine activity
- maternal supine hypotension
prolonged deceleration
- dec in FHR from baseline that is > 15 bpm lasting > 2 min (< 10 min)
- disruption of oxygen transfer from environment to fetus
- commonly seen during maternal pushing
sinusoidal pattern
- smooth, sine wave-like undulating pattern in FHR baseline with a cycle freq of 3-5 per min
- seen with fetal anemia
