Fetal Distress And Neonatal Hypoxic Acidosis during gestation and labour.

1. FETAL DISTRESS
Dr. Massam
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2. Objectives
a) Definition of fetal distress
b) Identify risk factors/causes of fetal distress
c) Describe pathogenesis of fetal distress
d) Describe clinical features and complications of fetal distress
e) Describe the differential diagnoses of fetal distress
f) Treat the patient according to guidelines of fetal distress
g) Describe preventive measures for fetal distress
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3. Introduction
• Fetal distress refers to the presence of signs in a pregnant woman
before or during childbirth that suggest that the fetus may not be
well.
• The term “fetal distress,” is believed to be too imprecise.
• They recommend instead “non-reassuring fetal status’’.
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4. Introduction…
• Non-reassuring fetal status is characterized by tachycardia or
bradycardia, reduced FHR variability, decelerations and absence of
accelerations (spontaneous or elicited).
• It must be emphasized that hypoxia and acidosis is the ultimate result
of the many causes of intrauterine fetal compromise
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5. Introduction…
• FHR patterns in labor are dynamic and can change rapidly from
normal to abnormal and vice versa.
• Because of this uncertainty about the diagnosis of fetal distress
terminologies used are “Reassuring” and “Non-reassuring” patterns
instead of fetal distress
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6. Definition
• Fetal distress is an ill-defined term, used to express intrauterine fetal
jeopardy, a result of intrauterine fetal hypoxia, Abnormal Fetal Heart
Rate patterns and Acidosis
While
• Non-reassuring fetal status is characterized by tachycardia or
bradycardia, reduced FHR variability, decelerations and absence of
accelerations (spontaneous or elicited).
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7. Epidemiology
• The overall risk of prompt caesarean delivery needed for fetal concern
was shown to be 3.1% in an unselected population.
• The risk exceeded 20% in patients with severe pre-eclampsia, post-
term or fetal growth-restricted fetuses with abnormal Doppler studies
and also in women with moderate/severe asthma or severe
hypothyroidism.
• The vast majority of cases of cerebral palsy in otherwise normal-term
infants are not associated with intrapartum hypoxia-ischaemia.
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8. Classification/Types
• There are two types of fetal distress
• Acute
• Chronic
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9. Classification/Types cont.…
• A. ACUTE:
i. During pregnancy — less common
• Placental separation in placenta previa or abruptio placentae
• Following external cephalic version due to cord entanglement
• During oxytocin induction
• Placental abruption
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10. Classification/Types…
ii. During labor — common
• Uterine hyper stimulation following oxytocin for augmentation of labor
• Uterine rupture or scar dehiscence
• Cord prolapse
• Injudicious administration of analgesics and anesthetic agents
• Maternal hypotension – as in epidural analgesia
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11. Classification/Types…
• B. CHRONIC
• The various clinical conditions which are responsible for chronic
placental insufficiency and IUGR, are also linked with chronic fetal
distress
• These conditions are divided into 4 groups
• Maternal
• Fetal
• Placental
• Unknown
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12. Classification/Types…
• Maternal
• Maternal nutrition before and during pregnancy
• Maternal diseases: Anemia, hypertension, thrombotic diseases, heart disease,
chronic renal disease, collagen vascular disease
• Toxins—Alcohol, smoking, cocaine, heroin, drugs
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13. Classification/Types…
• Fetal
• There is enough substrate in the maternal blood and also crosses the
placenta but is not utilized by the fetus due to—to—
• (1) Structural anomalies either cardiovascular, renal or others.
• (2) Chromosomal abnormality.
• (3) Infection TORCH agents (toxoplasmosis, rubella, cytomegalovirus and
herpes simplex) and malaria.
• (4) Multiple pregnancy—There is mechanical hindrance to growth and
excessive fetal demand.
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14. Classification/Types…
• Placental
• The causes include cases of poor uterine blood flow to the placental site for a
long time. This leads to chronic placental insufficiency with inadequate
substrate transfer.
• The placental pathology includes: Placenta previa, Abruption, Circumvallate,
Infarction and Mosaicism.
• Unknown: The cause remains unknown in about 40 per cent.
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15. Causes/Risk factors
• Maternal hypoxia
• Anaesthesia
• Heart failure
• Severe anaemia
• During eclamptic fits
• Severe pulmonary disease
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16. Causes/Risk factors…
• Placental (placental compression)
• Prolonged labor,
• Tonically contracted uterus,
• Placental separation,
• Uteroplacental insufficiency
• Improper / inadequate trophoblastic invasion and placentation in the first trimester,
• Lateral insertion of placenta, reduced maternal blood flow to the placental bed,.
• Foetoplacetal insufficiency
• Vascular anomalies of placenta and cord,.
• Decreased placental functioning mass (Small placenta, abruptio placenta, placenta
previa, post term pregnancy.)
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17. Causes/Risk factors…
• Obstetrical
• True knot
• Tight coiling around fetal neck
• Rupture of vasa previa
• Hematoma of cord
• Prolonged compression of head of fetus –compression of respiratory center
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18. Activity: Brainstorm
• What is the pathophysiology of fetal distress?
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19. Pathophysiology
• Under normal conditions when oxygen supply is adequate, aerobic
glycolysis occurs in the fetus and glycogen is converted into pyruvic
acid which is ultimately oxidized via the Kerb's cycle.
• During hypoxia when Oxygen saturation falls below 40%, anaerobic
glycolysis occurs, resulting in the accumulation of lactic acid and
pyruvic acid leading to metabolic acidosis.
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20. Pathophysiology Cont.…
• H-ions first stimulate and then depress the sinoatrial node leading to
tachycardia and bradycardia respectively.
• It also causes parasympathetic stimulation leading to hyperperistalsis
and relaxation of the anal sphincter with passage of meconium.
• Decreased fetal oxygenation in labor → hypoxia → metabolic acidosis
→ asphyxia → tissue damage/fetal death
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21. Diagnosis and Clinical Features
• Clinical suspicion: when decreased fetal movements are felt by the
mother or there is a slowing or stopping of the growth of serial
symphysis fundal height.
• Abnormal sonographic biometric parameters when IUGR or
macrosomia is suspected.
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22. Diagnosis and Clinical Features…
• Doppler ultrasound is particularly valuable when performed up to 34
weeks of gestation:
• Umbilical artery Doppler may detect changes that reflect increasing placental
vascular resistance.
• Fetal arterial Doppler of, for example, the middle cerebral artery, may detect
reduced resistance which has developed to maintain blood flow to the fetal
brain when placental function is impaired.
• Fetal venous Doppler may detect changes indicative of impaired cardiac
function and fetal acidosis.
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23. Diagnosis and Clinical Features…
• Cardiotocography (CTG) shows the fetal heart rate response to fetal
movement and to maternal contractions.
• The trace it produces may be described as reassuring, non-reassuring
or abnormal:
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24. Diagnosis and Clinical Features…
• Antenatal CTG:
• A normal fetal heart rate accelerates with fetal movement and is described as
reactive.
• Stillbirth rates have been shown to be significantly lower after a reactive trace
than after a non-reactive trace
• CTG interpretation is open to inter- and intra-observer variation but can be
interpreted by computerized analysis.
• CTG should not be used as the only form of surveillance of a high-risk
pregnancy
• A contraction stress test, carried out during induced contractions using
oxytocin, has no clinical benefits, and a false positive rate as high as 50%; it
may also have significant adverse effects
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25. Diagnosis and Clinical Features…
• Intrapartum CTG:
• See the separate Intrapartum Fetal Monitoring article for details.
• CTG should not be used routinely as part of the initial assessment of low-risk
women in early labor
• No decision about a woman's care should be made on the basis of CTG
findings alone.
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26. Diagnosis and Clinical Features…
• Biophysical profile (BPP) is time-consuming and rarely abnormal in
the presence of normal umbilical arterial Doppler.
• It consists of a combination of CTG, fetal behaviour (including movement,
tone and breathing) and amniotic fluid volume.
• This produces a BPP score to predict the degree of any compromise to the
fetus.
• Available evidence does not support its routine use in high-risk pregnancies
but observational data suggest it has good negative predictive value for fetal
compromise
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27. Diagnosis and Clinical Features…
• Amniotic fluid volume, both oligohydramnios and polyhydramnios,
has been shown to be associated with poor fetal outcomes.
• However, oligohydramnios is itself associated with intrauterine growth
restriction and urogenital malformations, which were not controlled for in the
studies, demonstrating an association with poor outcomes.
• Polyhydramnios, when clinically apparent, is related to poor neonatal
outcomes but mild, idiopathic polyhydramnios, detected only on ultrasound,
is not associated with adverse outcomes.
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28. Diagnosis and Clinical Features…
• Fetal scalp blood sampling during labor, to measure lactate (in
preference to pH if available), may be indicated for an abnormal
intrapartum CTG
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29. Investigations
• Obstetrics ultrasound
• Doppler Ultrasound
• Fetal scalp blood sampling
• Amniotic fluid volume measurement
• Biophysical profile (BPP)
• Fetal scalp blood sampling
• Cardiotocography (CTG)
• Antenatal CTG:
• Intrapartum CTG
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30. Treatment and Management
• Lateral positioning avoids compression of vena cava and aorta by the
gravid uterus. This increases cardiac output and uteroplacental
perfusion.
• Oxygen is administered (6-8 L/min) to the mother with mask to
improve fetal SaO2.
• Correction of dehydration by IV fluids (crystalloids) improves
intravascular volume and uterine perfusion.
• Correction of maternal hypotension (following epidural analgesia)
with immediate infusion of 1L of crystalloid (Ringer’s solution).
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31. Treatment and Management…
• Stoppage of oxytocin to improve fetal oxygenation. Fetal hypoxia may
be due to strong and sustained uterine contractions. With reassuring
FHR and in absence of fetal acidemia, oxytocin may be restarted.
• Tocolytic (Inj terbutaline 0.25 mg SC) is given when uterus is
hypertonus and there is nonreassuring FHR
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32. Treatment and Management…
• Amnioinfusion: this is the process to increase the intrauterine fluid
volume with warm normal saline (500mL).
• Indications are:
• (a) Oligohydramnios and cord compression
• (b) To dilute or to wash out meconium
• (c) To improve variable or prolonged decelerations. Advantages: Reduces cord
compression, meconium aspiration, and improves Apgar score. It also reduces
cesarean section rate.
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33. Treatment and Management…
• If the fetal heart rate pattern remains non-reassuring, further tests
are performed to rule out metabolic acidosis.
• Tests are: (i) To detect FHR accelerations (CTG) (ii) Scalp blood pH, (iii)
Fetal pulse oximetry,
• If acidosis is excluded → labor is monitored with repeat testing (every
30 min) to exclude acidosis.
• If the fetus is acidaemic → urgent delivery by safest method (vaginal
or abdominal) depending on the individual case
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34. Treatment and Management…
• SURGICAL: Cesarean delivery should be done with a 15° lateral tilt till
the baby is delivered. Thirty minutes has been accepted as the gold
standard for decision to delivery interval in cases of confirmed fetal
compromise.
• Pediatrician should be made available
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35. Treatment and Management…
• Fetal condition at birth is assessed by blood gas values of the
umbilical artery.
• Normal (mean) values are:
• pH 7.27, PCO2 50;
• HCO–3 23, base excess – 3.6.
• The correlation between the FHR and long term neurological
sequelae is poor.
• In many cases asphyxia occur prior to labor.
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36. Complications
• Intra Uterine Growth Restriction (IUGR)
• Fetal movement decrease
• Oligohydramnios
• Meconium stained amniotic fluid
• Intra Uterine fetal death (IUFD)
• Hypoxic ischemic encephalopathy
• Meconium aspiration syndrome
• Acidosis with decompensation
• Cerebral palsy
• Neonatal seizures
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37. Key Points
• Fetal distress is an ill-defined term, used to express intrauterine fetal
jeopardy, a result of intrauterine fetal hypoxia, Abnormal Fetal Heart
Rate patterns and Acidosis
• Important investigations are Obstetrics ultrasound, Doppler
Ultrasound, Fetal scalp blood sampling, Amniotic fluid volume
measurement, Biophysical profile (BPP), Fetal scalp blood sampling,
Cardiotocography (CTG)
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38. Evaluation Questions
1. What is Fetal Distress?
2. What are the causes of Fetal Distress?
3. What are the complications of fetal Distress?
4. What is the management for Fetal Distress?
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39. Key Reference
i. Gynecology by Ten teachers
ii. Jones, D. (1992), Fundamentals of Obstetrics and Gynecology, 1sted,
ELBS
iii. Massawe R, et al, Management of Obstetrics Emergencies and
Obstetrics, 1984
iv. Myles, M. (1999), Textbook for Midwives, 13thed, Churchill Livingstone
v. Obstetrics and Gynecology by Dutta
vi. Obstetrics by Ten teachers
vii. MoHCDGEC/ NACTE (2016). Curriculum for Technician Certificate (NTA
Level 5) Curriculum, Dodoma.
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40. Self Study Assignment
• What are the difference between Fetal Distress and Asphyxia
neonatorum
• Describe in details the investigations for Fetal Distress
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