1-2009-fetalsurveillanceduringlabor-090507102900-phpapp01.ppt

Fetal surveillance

1. 1
Fetal Surveillance During Labor
Du Xue , PHD
Department of Obstetrics
& Gynecology
General Hospital of TianJin
Medical University

2. 2
Fetal Surveillance During Labor
----Epidemiology
To be an essential element of good obste
tric care because intrapartum hypoxia an
d acidosis may develop in any pregnancy.
On the basis of prenatal care
----20% to 30% :high risk
----and 50% of perinatal morbidity and
mortality occurs in this group
----50% normal

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4. 4
Mechanisms of fetal distress
Fetal arterial blood oxygen
tension is only 25±5mmHg
compared with adult values of
about 100 mmHg.
The rate of oxygen
consumption is twice of the
adult per unit weight, and its
oxygen reserve is only enough
to meet its metabolic needs
for 1 to 2 minutes.

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Blood flow from the maternal
circulation is momentarily inte
rrupted during a contraction.
Clinical and experimental data i
ndicate that fetal death occurs
when 50% or more of transpla
cental oxygen exchange is inte
rrupted.
Hypoxia can easily occur.
A normal fetus can withstand t
he stress of labor without suffe
ring from hypoxia because suffi
cient oxygen exchange occurs
during the interval between co
ntractions.
A fetus whose oxygen supply is
marginal cannot tolerate the st
ress of contractions and will be
come hypoxic.

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Changes under hypoxic conditions
Baroreceptors and chemoreceptors in the
central circulation of the fetus influent the
FHR by giving rise to contraction-related o
r periodic FHR changes.
The hypoxia will also result in anaerobic m
etabolism. Pyruvate and lactic acid accum
ulate, causing fetal acidosis.

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Methods of monitoring fetal heart rate
Meconium
Fetal blood sampling
Umbilical cord blood sampling
The Apgar scoring system
Nonstress test
Contraction stress test
Ultrasonic assessment
Biophysical profile testing
Fetal Surveillance During Labor
----methods

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Methods of monitorin
fetal heart rate
Auscultation of the
fetal heart:by
stethoscope or
Doppler probe
Continuous
Electronic fetal
monitoring
External monitoring
Internal monitoring

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Auscultation of the fetal heart is performed
every 15 minutes after a uterine contraction
during the first stage of labor.
Auscultation of the fetal heart is performed
at least every 5 minutes after a uterine
contraction during the second stage of labor.
By continuous electronic fetal monitoring,
early recognition of changes in heart rate
patterns
that may be associated with such fetal
conditions as hypoxia and umbilical cord
compression
would serves as a warning and enable the
physician to intervene to prevent fetal death
in uterus or irreversible brain injury.

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Methods of Electronic Fetal
Monitoring
External
Noninvasive method
Utilizes an ultrasonic transducer to mon
itor the fetal heart
Utilizes the tocodynamometer (toco) to
monitor uterine contraction pattern
Application directly impacts results of d
ata received

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Methods of Electronic Fetal
Monitoring
Internal Fetal Monitoring
Invasive
FHR is monitored via a fetal scalp
electrode (IFSE)
Uterine activity is monitored by an
intrauterine pressure catheter (IUPC)
A combination of external and
internal fetal monitoring is common
practice

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continuous reporting of FHR-UC on a two-channel strip
chart recorderby means of a monitor that prints result
s
----uterine contractions(UC): stress for the fetus
----FHR: alteration in FHR correlates with fetal oxygen
ation
In the clinical setting, internal and external techniques
are often combined
----FHR: by using a scalp electrode for precise heart ra
te recording
----UC:the external tocotransducer for contractions to
avoid or minimize possible side effects from invasive i
nternal monitoring
Electronic fetal monitoring

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Fetal Heart Rate Patterns
Baseline Assessment
Periodic Fetal Heart Rate
Changes related to UC

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Fetal Heart Rate Patterns
Basline Assessment
Rate Beats/min
normal 120-160
Tachycardia >160
Bradycardia <120
Fetal Heart Rate (in beats per minute)

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Fetal Heart Rate Patterns
Basline Assessment

Baseline variability
Short-time variability /beat-to-beat
variability: short-term variability reflects
the interval between either successive
fetal electrocardiogram signals or
mechanical events of the cardiac cycle
Long-term variability :Long-term
variability reflects the frequency and
amplitude of change in the baseline rate

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Short-time variability
beat-to-beat variability
Long-term variability

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Short-time variability /beat-to
beat variability
 Normal short-time variability fluctuates
between 5 and 25 bpm
 Variability below 5 bpm is considered to
be potentially abnormal
 When associated with decelerations a va
riability of less than 5 beats/minutes usu
ally indicates severe fetal distress

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Long-term variability
The normal long-term variability is 3 to
10 cycles per minute.
 Variability is physiologically decreased
during the state of quiet sleep of the
fetus,which usually lasts for about 25
minutes until transition occurs to
another state.

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Fetal Heart Rate Patterns
Periodic Fetal Heart Rate Changes
Three kinds of responses to uterine contractions
No change: The FHR maintains the same
characteristics as in the preceding baseline
FHR.

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Fetal Heart Rate Patterns
Periodic Fetal Heart Rate Changes
Three kinds of responses to uterine contractions

 Acceleration: The FHR increases
in response to uterine contractions.
this is normal response.

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Fetal Heart Rate Patterns
Periodic Fetal Heart Rate Changes
Three kinds of responses to uterine contractions
Deceleration: The FHR decreases in response to
uterine contractions. Decelerations may be
early, late, variable or mixed. All except early
decelerations are abnormal.

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Types of deceleration Patterns
Early deceleration (head compressio
n):
Late deceleration ( uteroplacental ins
ufficiency
Variable deceleration (cord compressi
on)
Combined or mixed patterns
Decreased beat-to-beat variability

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Types of deceleration Patterns--1
Early deceleration:(head compression)
Definition: The onset, maximum fall, and recover
y that is coincident with the onset, peak, and en
d of the uterine contraction.
Significance: This pattern is seen when engagem
ent of the fetal head has occurred. Early deceler
ations are not thought to be associated with fetal
distress.
 Mechanism: The pressure on the fetal head lead
s to increased intracranial pressure that elicits a
vagal response

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Types of deceleration Patterns--1
Early deceleration:(head compressio
n)

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Types of deceleration Patterns--1
Early deceleration:(head compressio
n)

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Types of deceleration Patterns--2
Late deceleration (uteroplacental insufficiency)
Definition:
---onset
---maximal
---decrease
---recovery
that is shifted
to the right in
relation to the
contraction.

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Types of deceleration Patterns--2
Late deceleration (uteroplacental insufficiency)
Significance:
---The severity is graded by
the magnitude of the decrease
and the nadir of the deceleration
---Fetal hypoxia and acidosis
are usually more pronounced
with severe decelerations
---generally associated with low sca
lp blood PH values and high base d
eficits, indicating metabolic acidosi
s from anaerobic netabolism

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Types of deceleration Patterns--3 Vari
able deceletation (cord compression)
Definition: This pattern has a variable time of onset
and a variable form and may be nonrepetitive

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Significance:
caused by umbilical
cord compression.
The severity is
graded by their
duration.
Types of deceleration Patterns—3
Variable deceletation (cord compression)

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Partial or complete compression of the cord cau
ses a sudden increase in blood pressure in the
central circulation of the fetus.
The bradycardia is mediated via baroreceptors
Fetal blood gases indicate respiratory acidosis
with a low PH and high CO
2.
When cord compres
sion has been prolonged, hypoxia is also presen
t, showing a picture of combined respiratory an
d metabolic acidosis in fetal blood gases
Types of deceleration Patterns—3
Variable deceletation (cord compression)

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A flat baseline can be the result of s
everal conditions:
•Fetal acidosis
•Quiet sleep state
•Matermal sedation with drugs
Types of deceleration Patterns—4
Decreased beat-to beat variability

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Strategies for intervention--1
Attentions
A normal FHR pattern on the electronic monitor indic
ates a greater than 95% probability of fetal well-bein
g
Abnormal patterns may occur, however, in the absen
ce of fetal distress. The false-positive rate (i.e., good
Apgar scores and normal fetal-acid-bade status in th
e presence of abnormal FHR patterns) is as high as 8
0 %
Electronic fetal monitoring is a screening rather than
a diagnostic technique, because of the high false-pos
itive rate

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the clinical circumstance
the maternal condition
the stage of labor
Strategies for intervention--1
general considerations

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A change in maternal position can relieves fetal
pressure on the cord
100% oxygen by face mask to the mother
Oxytocic infusion should be discontinued
Elevating the presenting part by vaginal examin
ation
placing the mother in the trendelenburg positio
n if the pattern is persistent
 Use tocolytic agent to diminish uterine activity
Strategies for intervention--2
Variable Decelerations

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during the second stage of labor
aminioinfusion can decrease both the freq
uency and severity of variable deceleratio
ns
The benefit of aminioinfusion results in re
duced cesarean deliveries for fetal distres
s and fewer low Apgar scores at birth wit
hout apparent maternal or fetal distress
Strategies for intervention--2
Variable Decelerations

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The safest intervention to deliver the fetus wit
h cord compression is often low or outlet force
ps.
When progressive acidosis occurs , as determin
ed by serial scalp blood PH determinations, ce
sarean section should be performed if vaginal
delivery is not imminent
Prolonged deceleration requires
immediate intervention (FHR
falls to 60 to 90 bpm for
more than 2 minutes)
Strategies for intervention--2
Variable Decelerations

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Need further evaluation because it may be assosiated
with fetal acidosis
acoustic stimulation can be used to try to induce FHR-
accelerations
A response of greater than 15 bpm lasting at least 15
seconds can ensures the absence of fetal acidosis
The chance of acidosis occurring in the fetus who fails
to respond to such stimulation is about 50%

Strategies for intervention--3
Nonreactive fetal heart rate tracing

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Change the maternal position from supine to left or
right lateral
Give oxygen by face mask, this can increase fetal Po
2
by 5 mmHg
Stop any oxytocic infusion
Inject intravenously a bolus of tocolytic drug to relie
ve uterine tetany.
Monitor maternal blood pressure

Operative delivery should be considered for fetal diOperative delivery should be considered for fetal di
stress when fetal acidosis is present or when late destress when fetal acidosis is present or when late de
celerations are persistent in early labor and the cervcelerations are persistent in early labor and the cerv
ix is insufficiently dilatedix is insufficiently dilated
Strategies for intervention--4
Late Decelerations

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Prolonged periods of tachycardia are
usually associated with elevated maternal
temperature or an intrauterine infection,
which should be ruled out.
The acid-base status is usually normal
In general, fetal tachycardia occurs to
improve placental circulation when the
fetus is stressed.
Not a reliable change of the fetal distress
Strategies for intervention--4
Fetal Tachycardia

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Meconium
The presence of meconium in th
e amniotic fluid may be a sign of
fetal distress
Classification
----Early passage
----Late passge
----Management

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Meconium ----Early passage
occurs any time prior to rupture of the membra
nes and is classified as light or heavy, based on
its color and viscosity
light meconium: Light meconium is lightly stain
ed yellow or greenish amniotic fluid. It is not as
sociated with poor outcome
Heavy meconium: Heavy meconium is dark gre
en or black and usually thick and tenacious. It i
s associated with lower 1- and 5- minute Apga
r scores and is associated with the risk of meco
nium aspiration

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Meconium ----Late passge
Late passage usually occurs during the
second stage of labor, after clear amni
otic fluid has been noted earlier
Late passage, which is most often hea
vy, is usually associated with some ev
ent
----umbilical cord compression
----uterine hypertonus
----fetal distress.

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Meconium ----Management
 Amnioinfusion: it can decrease in meconium-related res
piratory complications perhaps as a result of the dilutiona
l effect of the infused fluid
Manner:
Infuse a bolus of up of up to 800 ml of normal saline
at a rate of 10-15 ml/minute over a period of 50 to 80
minutes. This is followed by a maintenance dose of 3
ml/minutes until delivery
Overdistention of the uterine cavity can be avoided by
maitaining the baseline uterine tone in the normal ran
ge and at less than 20mmHg

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Fetal Blood Sampling
PH :7.25-7.30
Indication:
clinical parameters
suggesting fetal distress:
----heavy meconium
----moderate to severely abnomal FHR patter
ns
Fetal Blood PH predicts neonatal outcome 82
% of the time , as measured by the Apgar sco
re.
The false-positive nate is about 8%, and the
false-negative about 10%

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Umbilical cord blood sampling
If there have been problems during the deliver
y or concern with the infant’s condition,obtain
an umbilical atery blood specimen for PH and a
cid-base determination is a syringe flushed wit
h heparin.
If a specimen cannot be obtained from the um
bilical artery ,obtain a specimen from an atery
on the chorionic surface of the placenta.

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Ultrasonic Doppler velocimetry
For blood flow measurements in umbilical and feta
l blood vessels, and percutaneous umbilical bolld
sampling (PUBS) have been used antepartum but
are generally not feasible methods for labor mana
gement.
Attention: Newborn cerebral dysfunction, manifes
ted as seizures and attributable to true birth asph
yxia, does not seem to occur unless the Apgar sco
re at 5 minutes is 3 or less, the umbilical artery bl
ood PH is less than 7,and resuscitation is necessar
y at birth.

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The Apgar scoring system
The Apgar score is an excellent tool for
assessing the overall status of the newb
orn soon after birth (1 minute) and after
a 5 minutes period of observation.
A normal Apgar score is 7 or greater at
1minute and 9 or 10 at 5 minutes.
Conditions result in low scores include
Asphyxia (implies hypoxia of sufficient degre
e to cause metabolic acidosis)
Prematurity
maternal drug administration

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Questions
The methods of monitoring the fetal
heart rate
Fetal heart rate patterns
Classification of meconium
Normal level of fetal blood PH

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