2. Physiology of fetal heart function
Definition
Components
Examples
3. The average baseline FHR in a healthy fetus at
20 weeks is 155 bpm (range 120-180 bpm)
Controlled by :
- sympathetic
- parasympathetic
As the parasympathetic matures with
advancing gestational age, the resting heart
rate ↓.
At term, the average FHR is 140 beats per
minute and the normal range is 120-160
bpm.
4. Vagus nerve
- sympathetic
- parasympathetic
although the fetal heart is innervated by the
sympathetic system as well, parasympathetic
input maintains baseline heart rate.
Parasympathetic stimulation becomes
dominant over sympathetic input as the fetus
develops which is why the FHR is initially
faster when 1st detectable and slows as the
fetal matures.
5. Vagal stimulation induces variability in the
time interval between each beat secondary to
influences on the vagus in the CNS :
baroreceptors, chemoreceptors
CNS influences the FHR via an intergrative
center in the medulla oblongata where the
vagus nerve originates.
During fetal sleep, the oscillatory variation in
the FHR diminishes and the variability around
the baseline beat has less amplitude
6. commonly known as an electronic fetal monitor
or external fetal monitor (EFM) or non-stress test
(NST)
measures simultaneously both the fetal heart rate
and the uterine contractions,
two separate disc-shaped transducers laid
against the woman's abdomen.
- ultrasound transducer measures the fetal
heartbeat.
- pressure-sensitive transducer
(tocodynamometer (toco) - measures the
strength and frequency of uterine contractions
7.
8.
9. detect early fetal tendency to produce
distress resulting from false-positive results
fetal hypoxia and Increase LSCS statistic
metabolic acidosis
closer assessment of
high-risk mothers
Benefits Risks
11. Normal CTG trace
Baseline heart rate: 110-160
Baseline variability : 5-15 bpm
Accelerations: 2 or more in 20 minutes. Each
of at least 15 bpm lasting at least 15s
Deceleration: absent
15. normal FHR at term 110 – 160 bpm
average fetal heart rate is considered to be
the result of tonic balance between
accelerator ( sympathetic ) and decelerator
(parasympathetic) influences on pacemaker
cells mediated via vagal slowing of heart rate
Heart rate also is under the control of arterial
chemoreceptors such that both hypoxia and
hypercapnia can modulate rate.
16. More severe and prolonged hypoxia, with a
rising blood lactate level and severe
metabolic acidemia, induces a prolonged fall
of heart rate due to direct effects on the
myocardium.
17. Fetal tachycardia – baseline >160 bpm over 10 minutes or more
- can be nonpathologic, considered a normal rate in the
premature fetus
Causes :
- maternal :
- chorioamnitis
- other causes of infection causing fever
- use of B-sympathomimetics
- fetal
- cardiac arrhythmias
- fetal anemia
- acute fetal blood loss
- abnormal fetal conduction system
18. FIGURE 4. Fetal tachycardia that is due to fetal
tachyarrhythmia associated with congenital
anomalies, in this case, ventricular septal defect.
Fetal heart rate is 180 bpm. Notice the "spike"
pattern of the fetal heart rate.
19. Fetal bradycardia – baseline heart rate <
110bpm for greater than 10 minutes.
Rate : 100 - 119 beats/min, in the absence of
other changes, usually is not considered to
represent fetal compromise.
Such low but potentially normal baseline
heart rates also have been attributed to vagal
response to head compression from occiput
posterior or transverse positions, particularly
during second-stage labor (Young and
Weinstein, 1976).
21. Causes of fetal bradycardia
Decreased in Decrease placental Impaired uterine Decreased maternal
umbilical blood flow exchange area blood flow oxygenation
•Cord compression •Abruptio placenta •Acute maternal •Apnea secondary to
•Cord prolapse •Uterine rupture hypotension seizures
•Excessive uterine
contraction
22.
23.
24. Defined as fluctuations in the FHR baseline of
2 cycles/min or greater with irregular
amplitude and inconstant frequency.
The time interval between 2 heartbeats in a
healthy fetus is seldom the same.
Normal : 5 – 15 bpm
This variability is secondary to the interaction
of the sympathetic and parasympathetic
reflexes
25.
26. Causes of loss of variability :
- fetal sleep
- administration of drugs
- narcotics, barbiturates, phenothiazines
- MgSO4
- gestational age (28-30wks)
- metabolic acidemia
27. Upward deflection in the baseline fetal heart
rate of at least 15 bpm lasting for at least 15
seconds.
In pregnancies of fewer than 32 weeks of
gestation, accelerations are defined as having
a peak 10 beats per minute or more above
the baseline and duration of 10 seconds or
longer.
28.
29. Reductions in fetal heart rate of at least
15bpm lasting for at least 15 seconds
4 types :
- Type 1 (early)- physiological
- Type 2 (late)- pathological
- variable
- prolonged
30. consists of a gradual decrease and return to
baseline associated with a contraction.
Result of a physiologic chain of events that
begins with head compression during a
uterine contraction
the degree of deceleration is generally
proportional to the contraction strength and
rarely falls below 100 to 110 beats/min or 20
to 30 beats/min below baseline.
31. early decelerations are not associated with
fetal hypoxia, acidemia, or low Apgar scores
32.
33. FIGURE 5. Early deceleration in a patient with an
unremarkable course of labor. Notice that the onset and the
return of the deceleration coincide with the start and the
end of the contraction, giving the characteristic mirror
image.
34. smooth, gradual, symmetrical decrease in
fetal heart rate beginning at or after the peak
of the contraction and returning to baseline
only after the contraction has ended.
The magnitude of late decelerations is rarely
more than 30 to 40 beats/min below baseline
and typically not more than 10 to 20
beats/min.
Late decelerations usually are not
accompanied by accelerations.
38. Inconsistent time of onset when compared to
uterine contraction
The onset of deceleration commonly varies
with successive contractions .
The duration is less than 2 minutes.
represent fetal heart rate reflexes that reflect
either blood pressure changes due to
interruption of umbilical flow or changes in
oxygenation
39. significant variable decelerations are those
decreasing to less than 70 beats/min and
lasting more than 60 seconds.
Causes :
- Umbilical cord entanglement
- Eg:
- Umblilical around body or neck
- True knot in the umbilical cord
- Prolapsed umbilical cord
40.
41. isolated deceleration lasting 2 minutes or
longer but less than 10 minutes from onset
to return to baseline.
Causes :
1) Total umbilical cord occlusion (cord
prolapse)
2) Maternal hypotension
3) Uterine hypertonia
4) VE or artificial ruptured of membrane
42.
43. regular, smooth, undulating form typical of a
sine wave that occurs with a frequency of 2-
5/minute and an amplitude range of 5-15
bpm
also characterized by a stable baseline heart
rate of 120 to 160 bpm and absent beat-to-
beat variability
Occurs in severe fetal anemia, as occurs in
cases of Rh disease or severe hypoxia
44.
45. Saltatory pattern :
- rapidly recurring couplets of acceleration
and deceleration causing relatively large
oscillations of the baseline fetal heart rate
- sympathetic stimulation overrides
parasympathetic dominance in response to
acute but temporary hypoxemia ( umbilical
cord compression )
- almost exclusively seen during labour
46. FIGURE 2. Saltatory pattern with wide
variability. The oscillations of the fetal
heart rate above and below the
baseline exceed 25 bpm.
47. Accelerations: absent for >40 minutes-first to
become apparent, and any of the following
Baseline heart rate
bradycardia<110 bpm
Tacycardia>150 bpm
Baseline variability:<10 bpm lasting for> 40 min,
greater significant if < 5 bpm
Decelerations: variable decelerations without
ominous features
48. Accelerations: absent for>40 min and any of the
following
Baseline heart rate: abnormal
Baseline variability:less than 5 bpm lasting for
>90 min
Deceleration
Repetitive late decelerations
Variable deceleration with ominous features(
duration >60s; beat loss>60 bpm;late recovery;
late deceleration component;poor baseline
variability btwn and/or during deceleration
52. Baseline FHR = 130 bpm
Variabilitiy = 5- 15 bpm
Have Acceleration
No deceleration
No contraction
CTG reactive
IMP: Normal Fetal Heart Rate
53.
54. BHR= 120 bpm
Variability 5 to 10 bpm
Prolonged deceleration
Contracting 2-3 in 10 minutes,varying in strenght
Deceleration occurs after VE;variability normal
before and after deceleration
55.
56. 1) BL=145-150 bpm
2) Variability < 5bpm
3) Early deceleration ( type 1 )
4) Contracting 5 in 10 minutes, lasting 90 s on
average
5) Head compression
6) Mx
Change maternal position
Reduce pitocin infusion
Continue observe trace for further abnormalities
57.
58. 1) Baseline FHR
1) Twin i=140-155 bpm
2) Twin ii=150-160bpm
2) Variability
1) Twin i 5-10bpm
2) Twin ii 5-10bpm
3) No deceleration
4) Contracting 3-4 in 10 minutes
5) Normal CTG for both twins.
59.
60. Baseline FHR = 130 bpm
Poor Beat to Beat Variability < 5 bpm
Have Acceleration
No Deceleration
Suspicious CTG
MX= Left lateral Position of the mother and
repeat CTG
61.
62. BHR = 160 bpm
Poor beat to beat variability < 5 bpm
No acceleration
Prolonged deceleration until 140 bpm and
occur more than 3 min.
No contraction
CTG not reactive
Imp: Acute fetal distress.
63.
64. BHR = 155 to 160 bpm
Poor Beat to Beat < 5 bpm
No acceleration in 20 min
No Deceleration
CTG not reactive
Acute Fetal distress
