Fetal echocardiography should be performed to evaluate for any structural heart defects, as supraventricular arrhythmias can sometimes be associated with congenital heart disease. Conservative management with close monitoring would be reasonable if the echocardiogram is normal. C-section and amiodarone are not indicated based on the information provided.

1. By Gebresilassie Andualem
Only @: https://t.me/OBGYN_Note_Book
May 2021
Intrapartum Assessment

2. Contents
Electronic Fetal Monitoring
Fetal Heart Rate Patterns
NICHD Classification & Interpretation
Fetal Monitoring in Low & High Risk Pregnancies
Other Intrapartum Assessment Techniques
Nonreassuring Fetal Status
Intrapartum Surveillance of Uterine Activity
2

3. Electronic Fetal Monitoring
• The primary goal (objective) of FHR monitoring
– is to assess the adequacy of fetal oxygenation and presence of fetal metabolic acidemia
during labor so that timely intervention can be undertaken to reduce the likelihood of
neurologic injury or death
• to prevent fetal injury that might result from interruption of normal fetal oxygenation during labor
– There is some evidence that intrapartum fetal monitoring is associated with a reduction in
intrapartum death. However, conclusive evidence of a reduction in long-term neurologic
impairment is lacking
• Universal fetal monitoring in labor
– increased incidence of abnormal FHR patterns and cesarean deliveries performed for fetal
distress
– does not reduce the incidence of perinatal asphyxia, low Apgar scores, or perinatal death
• Electronic fetal monitoring should be applied only to selected cases
• Electronic fetal monitoring has a high false-positive rate for predicting adverse neonatal
outcomes and may increase the rate of operative delivery
3

4. The oxygen pathway
• Fetal oxygenation
involves
– (1) the transfer of
oxygen from the
environment to the
fetus, and
– (2) the fetal response to
interruption of oxygen
transfer
4

5. Oxygen dissociation curve of hemoglobin
• tendency for hemoglobin to release oxygen is
increased by factors that signal an increased
requirement for oxygen
• oxygen release is enhanced by factors that
indicate active cellular metabolism. These
factors shift the oxyhemoglobin saturation
curve to the right and include
 by-products of anaerobic metabolism (reflected
by increased 2,3-diphosphoglycerate [DPG =
BPG] concentration),
• promotes hemoglobin transition from a high-oxygen-
affinity state to a low-oxygen-affinity state
 production of lactic acid (reflected by decreased
pH),
 by-products of aerobic metabolism (reflected by
increased partial pressure of carbon dioxide
[PCO2]), and
 heat
5

6. MECHANISMS OF PLACENTAL TRANSFER
6

7. Placental blood flow
• Aorta → common iliac
artery → internal iliac
(hypogastric) artery →
anterior division of
internal iliac artery →
uterine artery → arcuate
→ radial → spiral arteries
→ intervillous space of
the placenta
7

8. • Fetal PO2 and hemoglobin saturation values are low in comparison to
adult values, adequate delivery of oxygen to the fetal tissues is maintained
by a number of compensatory mechanisms
– fetal cardiac output per unit weight is greater than that of the adult
– Hemoglobin concentration and affinity for oxygen are greater in the fetus
– oxygenated blood is directed preferentially toward vital organs by way of
laminar blood flow and anatomic shunts at the level of the ductus venosus and
foramen ovale
• Conditions that can interrupt the transfer of oxygen from the
environment to the fetus at the level of the fetal blood
– fetal anemia and reduced oxygen carrying capacity secondary to
alloimmunization
– hemoglobinopathy, glucose-6-phosphate dehydrogenase (G6PD) deficiency,
– viral infections, fetomaternal hemorrhage, methemoglobinemia, or bleeding vasa
previa.
8

9. CAUSES OF INTERRUPTED OXYGEN TRANSFER
9

10. • Two commonly used modalities for intrapartum FHR monitoring are
1. Continuous electronic FHR monitoring and
– Internal (Direct) Electronic Monitoring
• accomplished by attaching a bipolar spiral electrode directly to the fetus (membrane ruptured)
• The wire electrode penetrates the fetal scalp, and the second pole is a metal wing on the electrode. The
electrical fetal cardiac signal - P wave, QRS complex, and T wave - is amplified and fed into a
cardiotachometer for heart rate calculation
– External (Indirect) Electronic Monitoring
• No rupture of membrane & use the ultrasound Doppler principle
• FHR is detected through the maternal abdominal wall using the ultrasound Doppler principle
• autocorrelation
2. Intermittent auscultation
• for 60 sec particularly before and immediately following a uterine contraction
– Fetoscope
– Handheld Doppler
• Contemporary evidence indicates that neither test performs better than the other, provided
that intermittent auscultation is performed as prescribed in randomized trials
10

11. 11

12. • Features of current fetal monitors include
– capability to monitor twin fetuses,
– monitor concurrent maternal heart rate,
– display the fetal ECG, and
– record maternal pulse oximetry values
• Limitations of EFM
– Poor for prediction & prevention of Hypoxic Injury
– no predictors of perinatal arterial ischemic stroke
– Fetal Head Compression: No randomized controlled trials, cohort studies, case control
studies, or other peer-reviewed studies in the literature support the hypothesis that fetal
head compression caused by uterine contractions or maternal pushing efforts can cause
local cerebral ischemia and hypoxic-ischemic injury in the absence of the established
mechanism of global hypoxia
12

13. • Which of the following is true of continuous fetal monitoring?
– A. It improves fetal outcome compared with intermittent auscultation.
– B. It provides an unbiased record of FHR during labor and delivery.
– C. It decreases cesarean delivery rates.
– D. It is employed in approximately 70% of obstetric units in the United States.
• Increasing use of electronic fetal monitoring has been associated with a
decrease in which adverse perinatal outcome?
– A. Death B. Neonatal seizures C. Cerebral palsy
– D. None of the above
• External tocodynamometer monitoring can reliably reveal all
EXCEPT which of the following regarding contractions?
– A. Onset B. Frequency C. Strength D. Resolution
13

14. Fetal Heart Rate Patterns
• Scaling factors recommended by the NICHD Workshop
– Vertical: 30 bpm per cm (range, 30 to 240 bpm)
– Horizontal: 3 cm/min chart recorder paper speed
 Scaling greatly affects the appearance of FHR
• Fetal heart rate variation is falsely displayed at the slower 1 cm/min paper speed compared with
that of the smoother baseline recorded at 3 cm/min
– Thus, pattern recognition can be considerably distorted depending on the scaling factors used
• FHR normally is increased or decreased by autonomic influences mediated
by sympathetic or parasympathetic impulses from brainstem centers
• Beat-to-beat variability is also under the control of the autonomic
nervous system
14

15. • During external ultrasound Doppler, reflected ultrasound signals from moving fetal heart
valves are analyzed through a microprocessor, which compares incoming signals with the
most recent previous signal. This process is called which of the following?
– A. Synchrony B. Correlation
– C. Transduction D. Autocorrelation
• Which peak wave voltage is the portion of the fetal electrocardiogram that is most reliably
detected?
– A. P-wave B. R-wave C. QRS complex D. T-wave
• With increasing fetal maturation, the baseline fetal heart rate (FHR) changes in
which of the following ways?
– A. Increased rate with decreasing variability
– B. Decreased rate with increasing variability
– C. Increased rate with increasing variability
– D. Decreased rate with decreasing variability
15

16. Electronic Fetal Monitoring Definitions
• Baseline Fetal Heart Changes
– refers to the modal characteristics which prevail
apart from periodic accelerations or decelerations
associated with uterine contractions
– Baseline – a mean FHR rounded to increments of 5
bpm during a 10-minutes segment excluding
accelerations, decelerations, and periods of marked
variability
• Normal (110–160), Tachycardia (> 160), Bradycardia:
(< 110)
1. Rate: Tachycardia,Wandering Baseline
2. Beat-to-Beat Variability: Increased / Decreased
3. Cardiac Arrhythmia
4. Sinusoidal Heart Rate
• Periodic Fetal Heart Rate Changes
– temporary deviations from baseline due to uterine
contractions
1. Accelerations
2. Deceleration
• Deceleration: Early / Late / Variable / Prolonged
16

17. 17
Character Description Pathology
Rate
• FHR is the result of
tonic balance between
– sympathetic &
parasympathetic
system
• hypoxia and
hypercapnia can
modulate rate arterial
chemoreceptors
• With increasing fetal
maturation, the heart
rate decreases
• Normal: 110–160 bpm
• Tachycardia: > 160 bpm (sympathetic system)
 Maternal fever (most common); Infection
 Medications (Sympathomimetics, Parasympatholytics,
Caffeine, Theophylline, Cocaine, Methamphetamine)
 Fetal anemia; Hyperthyroidism
 Arrhythmia (Sinus tachycardia, Supraventricular tachycardia,
Atrial fibrillation, Atrial flutter, Ventricular arrhythmia)
 Metabolic acidemia
• Bradycardia: < 110 bpm for at least 10 minutes
 Medications (Sympatholytics, Parasympathomimetics)
 Cardiac pacing and conduction abnormalities (Heart block,
Sjögren antibodies, Heterotaxy syndrome)
 Structural cardiac defects, Viral infections (e.g.,
cytomegalovirus)
 Fetal heart failure, Maternal hypoglycemia, Maternal
hypothermia
• Wandering Baseline (bn 120 and 160 bpm)
o suggestive of a neurologically abnormal fetus
o may occur as a preterminal event

18. • A 22-year-old woman, gravida 2, para 1, at 41 weeks of gestation, is laboring. Her cervix is dilated
to 8 cm and 100% effaced, and fetal vertex is at +1 station. Membranes have been ruptured for more
than 24 hours, and labor is being augmented with oxytocin. An amnioinfusion is running because of
3-4+ meconium. Fetal heart rate by scalp electrode has a baseline of 138 bpm with reduced short-
term variability and occasional mild variable decelerations. You are suddenly called to evaluate a
nonreas-suring fetal heart rate. The tocodynamometer shows six contractions in a 10-minute period
with a pressure of 70 mmHg, and fetal heart rate is now 70 bpm for more than 3 minutes. She is
placed in the left lateral position, oxytocin infusion is stopped, she is given oxygen by mask, and her
intravenous fluid rate is increased. Fetal heart rate is now 98 bpm. What is the best next step in
management?
– A. Cesarean section B. Vacuum delivery C. Ephedrine
– D. Knee-chest position E. Terbutaline
• This clinical scenario is describing hyperstimulation. Normal labor contractions have the following
properties: frequency—every 2 to 3 minutes; duration—45 seconds to a minute; intensity—up to 50
mm Hg. In this case, oxytocin has already been stopped, but the nonreassuring FHR pattern has not
resolved because oxytocin is still in the circulation. Thus, before taking the patient for a cesarean
section, terbutaline should be tried to reverse the hyperstimulation by tocolysis. This patient is not a
candidate for vacuum delivery (she is not even fully dilated yet). Ephedrine is not useful in this case.
The knee–chest position is sometimes more useful than the left lateral position when there is a
nonreassuring FHR pattern, especially a severe variable deceleration
18

19. 19
Character Description Pathology
Beat-to-Beat
Variability
• Fluctuations in the baseline
FHR that are irregular in
amplitude and frequency
• Oscillation - due to
sympathetic and
parasympathetic “push and
pull” regulation
• The phenomenon of
continuous R-to-R wave
FHR computation is known
as beat-to-beat variability
• Absent: amplitude range undetectable
• Minimal: ≤ 5 beats per minutes
 Reduced variability is the single most reliable sign of fetal
compromise
 Maternal analgesic drugs (common), CNS depressant drugs (Narcotics,
barbiturates, phenothiazines, tranquilizers, general anesthetics),
Corticosteroids, Meperidine, buprenorphine, Magnesium sulfate
 Severe maternal acidemia (eg – in diabetic ketoacidosis)
 NB: Silent oscillatory pattern refers to: baseline variability of FHR of
less than 5 bpm
• Moderate (normal): amplitude 6—25 beats per minute
• Marked: amplitude range > 25 beats per minute
o Physiological: fetal breathing and body movements; advancing
gestation
o Pathological: ??
Based on time interval between successive fetal R waves: Short & long term BBV (No clinical significance)

20. 20
Grades of baseline fetal heart rate variability
• 1. Undetectable, absent variability
• 2. Minimal variability, ≤5 bpm
• 3. Moderate (normal) variability, 6 to 25 bpm
• 4. Marked variability, >25 bpm
• 5. Sinusoidal pattern
• This differs from variability in that it
has a smooth, sinelike pattern of
regular fluctuation and is excluded in
the definition of fetal heart rate
variability

21. • Which of the following is not a cause of decreased beat-to-beat FHR variability?
– A. Diphenhydramine B. Meperidine C. Butorphanol D. Diabetic ketoacidosis
• Diminished variability in the FHR most likely represents which of the following?
– A. Hypoglycemia B. Hypoxia C. Hypercarbia D. Acidemia
• Which of the following describe early decelerations?
– A. Common during the active phase of labor B. Abrupt decrease (<30 seconds) to nadir
– C. Are associated with low Apgar scores D. Return to baseline slowly prior to the
end of a contraction
• Which of the following is most commonly associated with nuchal cord loops?
– A. True knots B. Neonatal jaundice C. Perinatal mortality
– D. Variable fetal heart rate decelerations
• Partial or complete cord occlusion leads to variable decelerations by which of the following
mechanisms?
– A. Increase in afterload (baroreceptor) followed by sudden increase in fetal arterial oxygen content
(chemoreceptor)
– B. Decrease in afterload followed by an increase in fetal arterial oxygen content
– C. Increase in afterload followed by a decrease in fetal arterial oxygen content
– D. Decrease in afterload followed by a decrease in fetal arterial oxygen content
21

22. 22
Character Description Pathology
Cardiac
Arrhythmia
• can only be documented,
practically speaking,
when scalp electrodes
are used
• little significance
• fetal anatomy and echocardiography
•  congenital heart block, Conduction defects
Sinusoidal
Heart
Rate
• Visually apparent,
smooth, sine wave-line
undulating pattern in
FHR baseline with a
cycle frequency of 3-5
per minute which
persists for ≥ 20 minutes
•  fetal intracranial hemorrhage, severe fetal asphyxia, and severe fetal anemia
•  severe fetal anemia  anti-D alloimmunization, Fetomaternal hemorrhage,
TTTS, fetal parvoviral infection, or vasa previa with bleeding
• also  chorioamnionitis, fetal distress, and umbilical cord occlusion
• Modanlou and Freeman (1982), based on their extensive review, proposed
adoption of a strict definition to define a sinusoidal pattern that is most likely
ominous
1. Stable baseline heart rate of 120 to 160 bpm with regular oscillations
2. Amplitude of 5 to 15 bpm (rarely greater)
3. Long-term variability frequency of 2 to 5 cycles per minute
4. Fixed or flat short-term variability
5. Oscillation of the sinusoidal waveform above or below a baseline
6. Absent accelerations

23. • For a patient who has labor pain, an abnormal NST mandates an
intermittent monitoring of FHR. Supraventricular arrhythmia is detected.
The fetus looks healthy by ultrasonography. AF is clear. What step should
be taken?
– A- fetal echocardiography B- C/S
– C- Conservative management D-amiodarone
• After epidural procedure for a pregnant woman the fetal heart rate shows
12-14 waves of sinusoidal waves with acceleration. With regard to the
following data, what is your management?:
• age: 26 yrs/ GA:36 wks/ dil:3 cm/ eff = 50%
– A) pregnancy termination for hypoxia
– B) this is pseudo sinusoidal pattern normal after epidural procedure. No
step is needed.
– C) change of position and oxygen to relieve pressure on the umbilical cord
– D) pregnancy termination for fetal hemorrhage
23

24. 24
Character Description Pathology
Acceleration
• rise in fetal heart rate above baseline
• always reassuring - confirm that the
fetus is not acidemic at that time
• ≥ 32 weeks: a peak of ≥ 15 bpm above
baseline, for ≥ 15 sec but < 2 minutes
from onset to return
• < 32 weeks: a peakOf ≥ 10 bpm above
baseline, for ≥ 10 seconds but < 2
minutes from onset to return
• Prolonged acceleration: lasts ≥2 minutes but
< 10 minutes in duration
• Baseline change: If an acceleration lasts ≥ 10
minutes

25. • Which of the following is the most common periodic FHR change?
– A. Early deceleration
– B.Acceleration
– C.Variable deceleration
– D. Late deceleration
• Which of the following is the most common fetal arrhythmia seen
intrapartum?
– A. Atrial tachycardia
– B. Sinus bradycardia
– C.Ventricular extrasystoles
– D.Atrial extrasystoles
25

26. 26
Character Pathology
Deceleration
-
at
least
15
beats/min
below
the
baseline
• drop below the baseline rate
1) Early  head compression – due to uterine contraction [(onset to nadir <30 seconds)]
o The nadir of the deceleration occurs at the same time as the peak of the contraction
o not associated with fetal hypoxia, acidemia, or low Apgar scores
o Dural stimulation → vagal nerve activation → heart rate deceleration
2) Late  uteroplacental insufficiency: (onset to nadir ≥ 30 seconds)
o the nadir of the deceleration occurring after the peak of the contraction
o hypotension from epidural analgesia and uterine hyperactivity from oxytocin stimulation
o Maternal diseases such as hypertension, diabetes, and collagen vascular disorders can cause chronic placental
dysfunction
o onset, nadir, and recovery of the deceleration occur after the beginning, peak, and ending of the contraction,
respectively
3) Variable  cord compression patterns: (onset to nadir <30 seconds)
o Duration: 15 seconds to 2 minutes; must be ≥ 15 bpm in amplitude
o Initial compression of the umbilical vein reduces fetal venous return and triggers a baroreceptor-mediated reflex rise in
FHR that commonly is described as a “shoulder”
o 2 mechanisms: cord occlusion produces - increase in afterload (baroreceptor) and drop in fetal arterial oxygen content
(chemoreceptor)
• Prolonged Deceleration: deceleration ≥ 15 bpm that lasts ≥ 2 minutes but < 10 minutes
o If a deceleration last ≥ 10 minutes, it is a baseline change
o  Uterine hyperactivity, cord entanglement, and maternal supine hypotension, Epidural, spinal, or paracervical
analgesia
o Significant decelerations are defined as late decelerations or variable decelerations that last > 60 seconds

27. 27
Early
Late
Variable fetal heart rate

28. Umbilical cord compression
• At term, the umbilical arteries receive 40% of fetal cardiac
output
• Early in a contraction
– Thin-walled umbilical vein
• decrease in fetal cardiac output leads to an initial compensatory rise in
fetal heart rate
• As cord compression intensifies,
– umbilical arteries are then also compressed
• The resulting rise in fetal systolic blood pressure leads to a vagal
mediated fetal heart rate deceleration
• As the contraction abates
– compression is relieved first on the umbilical arteries, elevated
fetal systolic blood pressures drop and the deceleration resolves
– A final increase in FHR is seen as a result of persistent
umbilical vein occlusion
– With completion of the uterine contraction and cord
compression, the fetal heart rate returns to baseline
28

29. • Which is wrong about late deceleration
– it occurs after the peak and nadir of uterine contraction
– lag phase represents fetal PO2 level not fetal blood PH
– the less the fetal PO2 before uterine contraction, the more is the lag phase before
deceleration
– reduced fetal PO2 level below critical level activates chemoreceptors and decelerations
• Which pattern is a sign of fetal distress in a 43 wk pregnant woman ?
– A) prolonged deceleration B-saltatory pattern
– C) Variable deceleration D- late deceleration
• In a 20 yr old woman of a PIH case, more than 50 % of uterine contractions are
accompanied with decelerations. What does this mean?
– A) Recurrent deceleration B) significant variable deceleration
– C ) prolonged deceleration D) long-term variability
29

30. • What drug does not reduce beat to beat variability?
– A) narcotics B) barbiturates C) phenothiazine
– D) in the first hour after MgSO4 administration
– Acidemia causes BTB variability reduction
– Hypoxia causes BTB variability increase
• Which is wrong about fetal heart rate deceleration?
– A- maternal HTN can cause chronic placental dysfunction and late deceleration
– B- early deceleration of 20 bpm of baseline shows fetal hypoxia and
acidemia
– C- increased afterload can activate chemoreceptors and cause late deceleration
• NST of a G2 / GA=37 wks/ cephalic presentation/ with a history of 2
IUFDs shows a 2-min deceleration. What is the best management
– A) daily BPP and observation B) C/S
– C) repeat of NST 24 hours later
– D) vaginal exam with continuous fetal monitoring
30

31. • If paper speed is 1 cm/min, this FHR
tracing depicts which of the following?
– A. Prolonged deceleration
– B. Late deceleration
– C. Early deceleration
– D. None of the above
31
• The FHR changes shown in the top panel of this image are
characteristic of which of the following?
– A. Late decelerations
– B. Early decelerations
– C. Variable decelerations
– D. Variable decelerations with rebound tachycardia

32. • Her cervix is dilated to 3 cm and 80% effaced, and fetal vertex is at 0 station.
The patient has requested regional anesthesia which is delivered via epidural
catheter. After placement, late decelerations are noted on the FHR monitor
with a reduction in variability. Maternal blood pressure is noted to be 90/60
which is below the baseline blood pressure noted on admission.What is the
best next step in management?
• A Change maternal position B Cesarean section
• C Maternal oxygen supplementation
• D Medication to improve maternal blood pressure EAmnioinfusion
– This clinical scenario is describing hypotension resulting from vasodilation that can
occur as a result of regional analgesia.The lower blood pressure results in
decreased perfusion to the uterus, which can cause a nonreassuring FHR (in this
case, late decelerations). It is possible to rectify the perfusion issue to the uterus by
adjusting the maternal position, which may decrease the pressure placed on the
vena cava by the gravid uterus, but this is not the best answer
– If reduced blood pressure is noted after placement of regional analgesia with
negative effect on the FHR tracing, prompt attention to maternal blood pressure is
warranted with medication to increase blood pressure.
32

33. • A 27-year-old woman, gravida 1, para 0, at 40 and 3/7th weeks of gestation, is in the middle of the
first stage of labor. Her cervix is dilated to 4 cm and a decision has been made to place an
epidural. Prior to placement of the epidural, she receives a 500-mL bolus of lactated Ringer's to
prehydrate her, and augmentation with oxytocin is begun. Her vitals are as follows:T = 99.1, BP =
110/74, P = 102, R = 18.The fetal heart rate baseline is 142 bpm with three accelerations every 20
minutes. She is contracting every 3 minutes.After placement of the epidural, fetal heart rate
baseline drops to 130 bpm, and no accelerations are seen within a 10-minute period.The fetal
heart rate also shows a gradual decline in the middle of each contraction to about 115 bpm and
then returns to baseline of 130 bpm. She has contractions every 2 to 3 minutes now. Her vitals at
this point are as follows:T = 99.2, BP = 78/56, P = 115, R = 18.What is the best next step in
management?
– A.Tylenol B. Penicillin C. Intravenous hydration D. Ephedrine E. Discontinue oxytocin
• One of the complications with placement of an epidural blockade is hypotension (before the
epidural BP = 110/74 and after the epidural BP = 78/56). An epidural blocks sympathetic discharge
to vessel walls, and vasoconstriction is inhibited.This causes blood to pool in dependent areas of
the body, thus decreasing venous return to the heart. Cardiac output decreases and subsequently
results in decreased uteroplacental circulation.To avoid hypotension, anesthesiologists hydrate
patients before placement of the epidural and then give ephedrine to keep the BP near its
baseline.Although the patient has a low-grade temperature (99.2°F), the fever is not the
cause of the nonreassuring fetal heart rate; therefore, neitherTylenol nor penicillin are the best
choices. Hyperstimulation is not the problem, so there is no need to discontinue the oxytocin.This
patient has already been prehydrated, so additional hydration would not be as efficacious as
giving ephedrine 33

34. • A 19-year-old woman, gravida 1, para 0, at 38 weeks of gestation, is in active labor. Her
cervix is dilated to 5 cm and fetal vertex is at + 1 station. The tocodynamometer displays
contractions every 2 to 3 minutes, lasting 1 minute, and producing 50 mm Hg of pressure
inside the uterus. The FHR by scalp electrode has a baseline of 140 bpm with random
sharp decelerations to 70 bpm that return to baseline in 60 to 80 seconds. When this type
of deceleration occurs, what is the best description of the initial acid–base status of the
fetus?
– A Respiratory acidosis B Metabolic acidosis C Uteroplacental insuffi ciency
– D Asphyxia E Increased PCO 2
• This clinical scenario is that of a severe variable deceleration. As the umbilical cord is
compressed, decreased perfusion of fetal tissue occurs. This causes the partial pressure of
carbon dioxide to increase and the partial pressure of oxygen to decrease. The increased
PCO2 decreases the pH, resulting in acidemia. The initial event is therefore respiratory
acidosis. When there is a prolonged decrease in perfusion, the fetus becomes dependent on
anaerobic (not requiring oxygen) glycolysis to meet its energy return and thus produces
pyruvic acid and lactic acid. This causes a further drop in the pH, resulting in metabolic
acidosis. Eventually, if the acidosis is unresolved, asphyxia occurs. Uteroplacental
insufficiency is a term that describes late decelerations. It does not describe the “acid–base”
status of the fetus. Although increased PCO 2 (one of the initial occurrences) contributes
to respiratory acidosis, it is not the best description of the fetal acid–base status
34

35. • During late decelerations, which of the following is true
regarding the FHR nadir?
– A. It is reached abruptly (<30 seconds), and FHR recovers to
baseline after the contraction.
– B. It is usually associated with accelerations.
– C. It is rarely more than 30–40 beats per minute in magnitude.
– D. It is reached gradually and occurs at the contraction peak,
and FHR recovers to baseline after the contraction.
35

36. 36
Other FHR patterns have been associated with umbilical cord compression
Character Description
Saltatory
• consists of rapidly recurring couplets of acceleration and deceleration causing
relatively large oscillations of the baseline FHR
• In the absence of other FHR findings, these do not signal fetal compromise
• almost invariably seen during rather than before labor
• Umbilical cord complications during labor
Lambda
pattern
• involving an acceleration followed by a variable deceleration with no
acceleration at the end of the deceleration
• This pattern typically is seen in early labor and is not ominous
• This lambda pattern may result from mild cord compression or stretch
Overshoot
• is a variable deceleration followed by acceleration.
• The clinical significance of this pattern is controversial
V-shaped VD • Umbilical cord compression due to oligohydramnios
W-shaped • cord compression due to a nuchal cord

37. Q: Which of the following statements regarding monitoring of FHR is true?
• A) A sinusoidal FHR pattern is almost invariably associated with an anemic,
asphyxiated fetus
• B) A saltatory FHR pattern is almost invariably seen during rather than before
labor
• C) The FHR tracing of the premature fetus should be analyzed by different
criteria than tracings obtained at term
– NB: The same relationship between the FHR pattern and the acid-base status has been
documented in preterm and term fetuses. Thus, both the antepartum and the
intrapartum FHR patterns of the premature fetus should be analyzed by the same
criteria used at term
• D) Fetuses with congenital anomalies will invariably exhibit abnormal FHR
patterns
– NB: The vast majority of fetuses with congenital anomalies have normal FHR patterns
and a response to asphyxia similar to that of the normal fetus
– Although no pathognomonic abnormal FHR patterns have been described for such
fetuses, the rate of cesarean sections for fetal distress is reported to be significantly
increased in this group. This may be explained by the oligohydramnios and fetal growth
retardation that commonly occur in pregnancies affected by fetal congenital anomalies.
37

38. Fetal Heart Rate Patterns During SSOL
• Decelerations
– virtually ubiquitous during SSOL
–  Both cord and fetal head compressions
– If decelerations <70 bpm ➔ 5-minute Apgar score decreased
• loss of beat-to-beat variability and baseline fetal heart rate <90 bpm predicted fetal
acidemia
• persistent or progressive baseline bradycardia / tachycardia was associated with lower
Apgar scores
38

39. NICHD Classification & Interpretation
• Clinical application of electronic FHR monitoring (EFM) consists of three interdependent
elements:
– (1) definition, that is, the words used to describe the FHR observations;
– (2) interpretation, or the physiologic significance of the FHR observations; and
– (3) management, or the clinical response to the FHR observations
• In 2008, the NICHD introduced a three-tier FHR classification system
– NICHAD: National Institute of Child Health and Human Development
• Category I
– Predictive of normal fetal acid-base balance at the time of observation
– All of the following criteria must be present
• Baseline rate: 110 to 160 bpm
• Moderate baseline FHR variability
• No late or variable decelerations
• Early decelerations may be present or absent
• Accelerations may be present or absent
39

40. • Category II
– FHR tracing does not meet criteria for either category I or III and is considered
indeterminate
– Baseline rate
• Tachycardia / Bradycardia not accompanied by absent baseline variability
– Baseline FHR variability
• Minimal baseline variability
• Absent baseline variability not accompanied by recurrent decelerations
• Marked baseline variability
– Accelerations
• Absence of induced accelerations after fetal stimulation
– Periodic or episodic decelerations
• Recurrent variable decelerations accompanied by minimal or moderate baseline variability
• Prolonged deceleration ≥ 2 min but < 10 min
• Recurrent late decelerations with moderate baseline variability
• Variable decelerations with other characteristics, such as slow return to baseline,
"overshoots," or "shoulders"
40

41. • Category III
– Predictive of abnormal fetal acid-base status at the time of observation
– include either (1) or (2) below.
• (1) Absent baseline variability and any of the following:
– Recurrent late decelerations
– Recurrent variable decelerations
– Bradycardia
• (2) Sinusoidal pattern
– Intervention: provision of supplemental oxygen, change in position,
treatment of hypotension, and discontinuation of any uterotonic drugs
being administered
41

42. • Which of the following is true of fetal scalp pH sampling?
– A. It is associated with a decreased cesarean delivery rate.
– B. It is commonly employed as an adjunct to continuous fetal monitoring.
– C. If the scalp pH is below 7.20, another scalp blood sample is collected immediately, and the
mother is moved to the operating room and prepared for surgery.
– D. It is advantageous over lactate sampling because of a higher procedural success rate.
• This ST-segment waveform analysis suggests which of the following?
– A. Metabolic acidemia
– B. Hypocarbia
– C. Progressive fetal hypoxia
– D. Normal ST-segment waveform change during latent labor
• One mechanism that is theorized to cause meconium passage by the fetus includes which
of the following?
– A. Vagal stimulation
– B. Fetal hyperglycemia
– C. Immature gastrointestinal peristalsis
– D. Increased gastrointestinal hyperosmolar load
42

43. • The American College of Obstetricians and Gynecologists
specifies that hypoxic ischemic encephalopathy due to
profound intrapartum hypoxia should also show other signs of
damage that includes which of the following?
– A. pH <7.1
– B. Base deficit >18 mmol/L
– C.Apgar scores of 0–5 beyond 5 minutes
– D. None of the above
43

44. • Essential criteria to define an acute intrapartum event sufficient to cause
cerebral palsy
– 1. Umbilical cord arterial blood pH <7 and base deficit ≥12 mmol/L
– 2. Early onset of severe or moderate neonatal encephalopathy in infants born at 34 or
more weeks of gestation
– 3. Cerebral palsy of the spastic quadriplegic or dyskinetic type
– 4. Exclusion of other identifiable etiologies such as trauma, coagulation disorders,
infectious conditions, or genetic disorders
• Criteria that collectively suggest the event occurred within 48 hours of birth
– 1. A sentinel hypoxic event immediately before or during labor
– 2. A sudden and sustained fetal bradycardia, or the absence of fetal heart rate variability
in the presence of persistent late or variable decelerations, usually after a hypoxic
sentinel event when the pattern was previously normal
– 3. Apgar scores of 0 to 3 beyond 5 min
– 4. Onset of multisystem involvement within 72 hr of birth
– 5. Early imaging study showing evidence of acute nonfocal cerebral abnormality
44

45. Categories of umbilical artery acidemia
45

46. Fetal Monitoring in Low & High Risk Pregnancies
46
Guidelines for Methods of Intrapartum Fetal Heart Rate Monitoring (AAP & ACOG (2017))

47. Other Intrapartum Assessment Techniques
• Fetal Scalp Blood Sampling
– measurements of the pH in capillary scalp blood may help identify the fetus in serious distress
• blood is collected into a heparinized glass capillary tube
– But, neither normal nor abnormal scalp pH results are predictive of neonatal outcome
– pH of fetal capillary scalp blood is usually lower than that of umbilical venous blood and
approaches that of umbilical arterial blood
– pH
• ≥7.25: observe labor; 7.20 - 7.25: repeat pH within 30 minutes; <7.20: Deliver promptly
– Scalp blood lactate: equivalent in predicting fetal acidemia
• advantage - smaller amount of blood is needed
• Scalp Stimulation
– heart rate acceleration in response to pinching the fetal scalp with an Allis clamp just before
obtaining blood was invariably associated with a normal pH
• reliable alternative to scalp blood pH determination
– But, failure to provoke acceleration – is not uniformly predictive of fetal acidemia
47

48. • Vibroacoustic Stimulation
– uses an electronic artificial larynx placed approximately 1 cm from or directly onto the
maternal abdomen
– Normal response: if a FHR acceleration of at least 15 bpm for at least 15 seconds
occurs within 15 seconds after the stimulation and with prolonged fetal movements
– effective predictor of fetal acidosis in the setting of variable decelerations. But, limited
in the setting of late decelerations
• Fetal Pulse Oximetry
– similar to that of adult pulse oximetry
– allows assessment of fetal oxyhemoglobin saturation once membranes are ruptured
– transcervical device - Normal: ≥ 30%
– saturation values <30 percent (persistent for ≥ 2 minutes) were associated with a
greater risk of potential fetal compromise
48

49. • Fetal Electrocardiography
– P-R and ST-Segment Analysis
• ST segment - reflects myocardial repolarization
• So myocardial hypoxia can lead to elevation of ST
segment & T wave
– mature fetus exposed to hypoxemia develops an
elevated ST segment and a progressive rise in the
T-wave height that can be expressed as a T:QRS
ratio
• Intrapartum Doppler Velocimetry
– abnormal Doppler waveforms may signify
pathological umbilical-placental vessel resistance
49

50. Nonreassuring Fetal Status
• Terminology
– Reassuring suggests a restoration of confidence in the health of the fetus by a particular pattern
– Nonreassuring: suggests inability to remove doubt
– Fetal distress: too broad and vague to be applied with any precision to clinical situations
• Diagnosis
– NICHD Three-Tier Fetal Heart Rate Interpretation System
– Incidence during labor
• Category I (normal FHR): in 99.5 percent of tracings
• Category II (indeterminate FHR): in 84.1 percent of tracings
• Category III (abnormal FHR): in ~ 0.1 percent
50

51. Meconium in the Amnionic Fluid
• 12 to 22% of labors are complicated by meconium
– only a few are linked to neonatal mortality
• @ Parkland Hospital,
– meconium was found to be a “low-risk” obstetrical hazard
– because the perinatal mortality rate attributable to meconium was only 1 death per 1000 live births
• occurs in approximately 2 to 10% of infants born through MSAF (UpToDate)
• Incidence varies with gestational age (UpToDate)
– Preterm: 5.1%; Term: 16.5%; Postterm: 27.1%
Nelson 21st Edition
• MSAF is found in 10–15% of births and usually occurs in term or postterm infants
– MAS develops in 5% of such infants;
• 30% require mechanical ventilation
• 3–5% die
• Usually, but not invariably, fetal distress and hypoxia occur before the passage of meconium
into amniotic fluid
51

52. • Three theories regarding fetal passage of meconium may explain
– In response to hypoxia - signals fetal compromise
– Due normal GI maturation under neural control
– Due to vagal stimulation from common but transient umbilical cord entrapment
with resultant increased bowel peristalsis
• Meconium consists
– Substances mainly derived from the digestive tract
– Including salivary, gastric, pancreatic and intestinal juices, mucus, bile, bile acids, cellular
debris, lanugo hairs, fetal wax and blood
– Notably, since meconium is located ‘extracorporeally (outside circulation)’, like the
whole content of the gastrointestinal tract, its constituents are hidden and normally not
recognized by the fetal immune system.
– Normally, meconium is sterile as the colon is inoculated with bacteria after delivery.
52

53. 53
Pathophysiology of meconium
passage and the meconium aspiration
syndrome
V̇/Q̇, Ventilation-perfusion ratio
• This proposed pathophysiological sequence
is not all-inclusive, because it does not
account for approximately half of the
cases of meconium aspiration syndrome
in which the fetus is not acidemic at
birth
• Meconium aspiration is unpredictable and
likely unpreventable
– clear amnionic fluid is poor predictor
(unreliable sign of fetal well-being)

54. • Growing evidence indicates that
– many newborns with meconium aspiration syndrome have suffered chronic hypoxia before
birth
– Blackwell and associates (2001) found that 60 percent of neonates diagnosed with meconium
aspiration syndrome had umbilical artery blood pH ≥ 7.2, implying that the syndrome was
unrelated to the neonatal condition at delivery
– Similarly, markers of chronic hypoxia, such as elevated fetal erythropoietin levels and increased
nucleated red blood cell counts in newborns,
• suggest that chronic hypoxia is involved in many meconium aspiration syndrome cases
54

55. • MAS has been defined by clinical criteria:
– (1) respiratory distress (tachypnoea, retractions or grunting) in a
neonate born through MSAF
– (2) a need for supplemental oxygen to maintain oxygen saturation of
haemoglobin (SaO 2 ) at ≥ 92%
– (3) oxygen requirements starting during the first 2 h of life and
lasting for at least 12 h
– (4) absence of congenital malformations of the airway, lung or heart
55

56. • Complication of Meconium aspiration syndrome
– fetal acidemia at birth
– cesarean delivery, forceps to expedite delivery, intrapartum heart rate abnormalities, depressed
Apgar scores, and need for assisted ventilation at delivery
56

57. • Current recommendation on management of a newborn with meconium-stained
amnionic fluid
– newborns with meconium-stained amnionic fluid, regardless of their vigor, should no
longer routinely receive intrapartum suctioning.
– Suctioning is reserved for those with airway obstruction
– appropriately credentialed team with full resuscitation skills should be available
57

58. NRFHR - Management Options
• correcting any fetal insult, if possible
– Correcting maternal hypotension caused by regional analgesia
– discontinuing oxytocin both serve to improve uteroplacental perfusion
• Tocolysis
– Terbutaline sulfate - single 250 μg IV/SC
– intravenous doses of nitroglycerin—60 to 180 μg
– Still,ACOG (2017b) cites that evidence is insufficient to recommend tocolysis for NRFHRPs
– Amnioinfusion
• Protocol: 500- to 800-mL bolus of warmed normal saline followed by a continuous infusion of approximately 3 mL/min
• Important in three clinical areas
– (1) treatment of variable or prolonged decelerations (ACOG (2016))
– (2) prophylaxis for women with oligohydramnios, as with prolonged ROM - to avoid cord compression
– (3) attempts to dilute or wash out thick meconium – [ACOG (2016) - not recommended]
• Vaginal examination excludes a prolapsed cord or impending delivery
• Supportive – to raise fetal oxygen saturation levels
– intravenous hydration: 500 to 1000 mL of lactated Ringer solution given over 20 minutes
– supplemental oxygen at 10 L/min using a nonrebreathing mask
58

59. • Complications Associated with Amnioinfusion from a Survey of 186 Obstetrical Units
59

60. • “ABCD” Approach (Gabbe 7th)
– Assess the Oxygen Pathway (Maternal)
– Begin Corrective Measures as Indicated
Conservative corrective measures
• Supplement oxygen
• Lateral maternal positioning (right or left)
• IV fluid: bolus of 500 to 1000 mL
• Correct maternal hypotension
• Reduce uterine activity – if hyperstimulation, hypercontractility, and tetanic contraction
• Amnioinfusion
• Alter second stage pushing and breathing technique
– open-glottis, rather than Valsalva-style, pushing;
– fewer pushing efforts per contraction;
– shorter individual pushing efforts;
– pushing with every other or every third contraction; and
– pushing only with perceived urge
– Clear Obstacles to Rapid Delivery
– Determine Decision-to-Delivery Time
60

61. • Some Resuscitative Measures for Category II or Category III Tracings
61

62. • ACOG (2014) has recommended umbilical cord blood gases be obtained whenever cesarean delivery is
performed for
– fetal compromise,
– a low 5-minute Apgar score,
– severe fetal-growth restriction,
– abnormal fetal heart rate tracing,
– maternal thyroid disease, or
– multifetal gestation
Benefits of Electronic Fetal Heart Rate Monitoring
• permits early detection of compromised fetus
• Cochrane Database review found that intermittent auscultation had a higher
cesarean delivery rate compared with continuous monitoring (Martis, 2017)
Current Recommendations
• a 1-to-1 nurse–patient ratio be used if auscultation is employed
62

63. • CTG during labour is associated with reduced rates of neonatal
seizures, but no clear differences in cerebral palsy, infant
mortality or other standard measures of neonatal wellbeing
• However, continuous CTG was associated with an increase in
caesarean sections and instrumental vaginal births
• The challenge is how best to convey these results to women to
enable them to make an informed decision without
compromising the normality of labour.
63

64. 64
• Using a hand‐held (battery and wind‐up) Doppler and intermittent CTG with an
abdominal transducer without paper tracing for IA in labour was associated with an
increase in caesarean sections due to fetal distress. There was no clear difference in
neonatal outcomes (low Apgar scores at five minutes after birth, neonatal seizures or
perinatal mortality). Long‐term outcomes for the baby (including neurodevelopmental
disability and cerebral palsy) were not reported. The quality of the evidence was assessed
as moderate to very low and several important outcomes were not reported which means
that uncertainty remains regarding the use of IA of FHR in labour.
• As intermittent CTG and Doppler were associated with higher rates of caesarean
sections compared with routine Pinard monitoring, women, health practitioners and
policy makers need to consider these results in the absence of evidence of short‐ and
long‐term benefits for the mother or baby.
• Large high‐quality randomised trials, particularly in low‐income settings, are needed.
Trials should assess both short‐ and long‐term health outcomes, comparing different
monitoring tools and timing for IA

65. Electronic Fetal Monitoring Complications
• Intrauterine pressure catheter
– May lacerate a fetal vessel in the placenta
– abruption, serious morbidity, and spurious recordings that have
resulted in inappropriate management
– Severe cord compression
– Injury to the fetal scalp or breech by a heart rate electrode – rare
– greater risk of infection
• relative contraindications to internal fetal monitoring
– maternal infections: HIV, HSV, and hepatitis B and C virus
65

66. Intrapartum Surveillance of Uterine Activity
• Old method
– Fluid-filled plastic catheter with its distal tip located above the
presenting part
• Modern method
1. Intrauterine Pressure Catheter
– catheter, contained within the introducer, is inserted into the
birth canal and placed along one side of the fetal head
– catheter is then gently advanced into the uterus, and introducer
is withdrawn
– can provide a more accurate assessment of contraction
duration, length, and strength
– Indications:
• In cases of FHR decelerations - to clarify the relationship between the
timing of the deceleration and the contraction
• allows an Amnioinfusion to be performed in cases of severe variable
fetal heart rate decelerations
– Contraindications: intact fetal membrane, placenta previa or
vasa previa, bleeding of unknown origin,
66
Types of IUPCs catheters —three
i. Transducer tip
ii. Air-coupled balloon sensor tip
iii. Fluid-filled

67. 2. External Tocodynamometry
– transducer button, or “plunger,” is held against the maternal abdominal wall
– measure tension across the abdominal wall and detect only contraction frequency and
duration
– affected by contraction strength, maternal habitus, position, GA, and monitor location
on abdomen
• External palpation
– subjective and requires the physical presence of a clinician to perform frequent
examinations
• Electrohysterography
– is a noninvasive technology that detects uterine electrical activity using electrodes
placed on the mother's abdominal wall
– may be as reliable and accurate as internal tocodynamometry, but it has not been
studied extensively.
67

68. • Routine use of IUPC is not recommended
• A large randomized trial of internal versus external
tocodynamometry for monitoring labor showed no difference
in rates of operative delivery or fetal outcomes between the
two groups
• Internal tocodynamometry is more costly and more invasive
and thus should be reserved for specific circumstances
68

69. • Contraction intensity
– defined as the rise in pressure above a resting pressure baseline
• Uterine performance
– is the product of contraction intensity in mm Hg multiplied by the number of
contractions in a 10-minute span
– Montevideo Units
• MVUs are calculated by subtracting the baseline uterine pressure from the peak uterine pressure
of each contraction in a 10-minute window of time and then taking the sum of these pressures
• Objective calculation of contraction strength (Montevideo units) is desirable to help determine
the cause of protracted or arrested labor
• Two hundred Montevideo units or more is considered adequate for normal labor progression
– No clear-cut division marks labor onset
• Uterine contractions usually are not associated with pain until their strength exceeds 15 mm Hg
• To distend the LUS and cervix, Braxton Hicks contractions should exceed 15 mm Hg
• Uterine activity increases gradually after 30 weeks
– Braxton Hicks
69

70. Origin and Propagation of Contractions
Pacemaker theory
• The normal contractile wave of labor originates near the
uterine end of one of the fallopian tubes.
– Thus, these areas act as “pacemakers”
• right pacemaker usually predominates over the left and starts
most contractile waves.
• Contractions spread from the pacemaker area throughout the
uterus at 2 cm/sec, and the whole organ is depolarized within
15 seconds
70

71. Uterine Contraction Terminology
• Normal uterine activity is defined as five or fewer
contractions in 10 minutes, averaged during a 30-minute
span
• Tachysystole: > 5 contractions in 10 minutes, averaged over
30 minutes
– spontaneous or induced labor
– The term hyperstimulation was abandoned
– Counts of ≥ 6 contractions in 10 minutes - significantly associated
with FHR decelerations
71