Cardiotocography , CTG , NST ,CST

3. a technical means of recording (-graphy) the fetal
heartbeat (cardio-) and the uterine contractions (-
toco-) during pregnancy or labour . The term used
to describe the monitoring is called a
cardiotocograph, commonly known as an electronic
fetal monitor (EFM).

4. 1 - Uterine Activity ( contractions ) :
Several factors assessing uterine contractions :
• Frequency : the amount of time between the start of
contraction to the start of next contraction
• Duration : the amount of time from the start of the
contraction to the end of the same contraction
• Intensity : measures the strength of contractions in
mm/Hg

5. 2 - Baseline Fetal Heart Rate :
between 120 – 160 bpm
Abnormalities :
Fetal bradycardia (FHR ˂ 110 bpm ) indicates :
1. Fetal Hypoxia. Bradycardia is a late sign of fetal
hypoxia (a continual lack of oxygen)
2. Medications. Medications such as narcotics cause
bradycardia by preventing receptor sites in the fetal
heart muscle from accepting epinephrine, which
works to increase heart rate
3. Maternal Hypothyroidism

6. Fetal bradycardia (FHR ˂ 110 bpm ) indicates :
4. Observed in epidural anesthesia ; Epidurals cause
vasodilation, which leads to an increase in the
incidence of maternal hypotension during labor
cause bradycardia indirectly due to a reflex
mechanism or as a result of hypotension
5. Synthetic Oxytocin may produce bradycardia by
causing a hyperstimulation of the uterine muscle
(myometrium), resulting in hypoxia

7. • Fetal tachycardia (FHR ˃ 160 bpm ) indicates :
1. Fetal Hypoxia. early sign of hypoxia
2. Maternal pyrexia
3. Fetal Infection. early sign of an intrauterine
infection (a stress reaction to sepsis).
4. Medications. ; Sympathomimetic ( ritodrine )
5. Prematurity. Due to immature CNS
6. Maternal Anxiety. During periods of maternal
stress and anxiety, epinephrine is released into the
mother’s blood stream that crosses the placenta,
resulting in an increase in fetal heart rate.

8. 3 - Variability :
the normal irregular changes and fluctuations in the
fetal heart rate.
Types :
Short term variability :
normally FHR changes by 5-10 bpm ( beat to beat
Variability )
Long term variability :
Long-term variability is fluctuations around the fetal
heart rate baseline

9. 3 - Variability :
Long-term variability can be divided into the following
categories:
Decreased variability: minimal variability (0-5 bpm).
Moderate variability: normal variability (6-25 bpm).
Marked variability: saltatory variability (<25bpm)

10. 3 - Variability :
Decreased variability may occur in the following
situations:
1. Hypoxia and acidosis
2. Prematurity
3. Fetal sleep
Loss of variability associated with :
1. Any fetal tachycardia
2. Intra amniotic infections
3. Fetal congenital anomalies

11. 3 - Variability :
Diminished or lost variability indicates depression of
brain stem centers controlling the interaction between
sympathetic and parasympathetic tones
Persistent minimal or absent variability is requiring
immediate inervention

12. 4- Accelerations :
transient increase in FHR of 15 bpm lasting for 15
seconds

13. 5- Decelerations :
decrease in FHR > 15 beats per minute for < 30 second
Types :
1. Early
2. Variable
3. Late.
4. Prolonged

14. 5- Decelerations :
• Early deceleration:
 begins at or after the onset of a contraction and
returns to the baseline rate by the time the
contraction has finished and produces a mirror
image of the contraction.
 Repetitive with uniform shape
 Onset-with Onset Of Contraction
 Duration-length Of Contraction
 Proposed Mechanism-head Compression

15. 5- Decelerations :
• Early deceleration:
 Early decelerations occur most frequently in the
following clinical situations:
 During sterile vaginal examinations
 In second stage of labor during pushing
 After amniotic sac has ruptured
 Common In Primigravidas

16. 5- Decelerations :
• Early deceleration:

17. 5- Decelerations :
Late Decelerations:
 Late decelerations are transitory decreases in heart
rate due to uteroplacental insufficiency
 The late deceleration begins after the onset of the
peak or middle of the contraction and ends after the
contraction

18. 5- Decelerations :
Late Decelerations: Causes of Late Decelerations :
1. Excessive uterine contractions, maternal
hypotension, or maternal hypoxemia.
2. Reduced placental exchange as in hypertensive
disorders, diabetes, IUGR, abruption

19. 5- Decelerations :
Late Decelerations: Management of Late Decelerations
1. Place patient on side
2. Discontinue oxytocin
3. Correct any hypotension
4. IV hydration.
5. Tocolysis
6. Administer O2 by tight face mask [25, 40]
7. If late decelerations persist for more than 30
minutes fetal scalp pH is indicated.

20. 5- Decelerations :
Variable decelerations :
• They may appear V-shaped or U-shaped not related
to contractions
• They mean umbilical cord compression
• They indicate possible compromise if they become
prolonged or are persistent
• May suggest oligohydraminos ( dangerous with IUGR
and postdate )

21. 5- Decelerations :
Variable decelerations :

22. Definition :
1ry screening test for fetal surveillance by
continuous electronic monitoring of the fetal heart
rate and observing its significant accelerations in
association with fetal movement perceived by the
mother

24. Principal : normally the fetal heart rate accelerates
in response to fetal movement

25. Performing NST :
1. Positioning the patient on semisetting on her back to
release the weight of the uterus from inferior vena cava
2. External monitor applied to the mothers abdomen for 20
minutes
3. Instruct the mother to press a button when she feels the
fetal movement
4. If no fetal movement recorded for 20 minutes : (
correction of hypoglyvemia if present - acoustic
stimulation to stimulate the fetal movement - external
manipulations of the fetus )

26. Results :
1. Reactive ( -ve test ) : when at least two or more
movement accompanied by accelerations of FHR of 15
bpm lasting for 15 seconds .Reactive NST means that the
fetus will survive safely for one week ( recently 3 days )
2. Non-Reactive NST ( +ve test ) : means absence of fetal
accelerations in response to fetal movement . ( should be
repeated next day after breakfast ) .normally non-reactive
before 30 weeks due to CNS immaturity .The test must be
repeated every 3 days in cases of : ( Unstable DM , SPET ,
Oligohydraminos ) The test must be repeated daily in
cases of PROM

27. Other Variations :
1. Uterine contractions recorded : evaluated as CST
2. Spontaneous decelaeration ( bad sign ) associated with 50
% fetal Distress
• Advantages :
• Has no contraindications ( can be done for any patient )
• Low false negative rate

28. • Disadvantages :
• Subjective test ( depend on maternal perception of fetal
movement )
• High false positive due to
1. maternal hypoglycemia
2. testing during the baby is sleep
3. maternal administration of alcohols or drugs
4. preterm baby

29. “ oxytocin challenge test “
• Indications : when NST is abnormal
• Performing CST :
• The same protocol as NST but physiological uterine
contraction is stimulated by :
1. Nipple stimulation for 10 min till contractions occur
2. Diluted oxytocin start by 0.5 mu/min then ↑ every 15-20
min
3. Contractions are satisfactory when reached 3-5 / 10 min
lasting for 45 sec

30. “ oxytocin challenge test “

31. • Principal :
Uterine contraction  compresses spiral arterioles 
oxygen to the fetus
If :
Good metabolic reserve  no hypoxia , no late decelerations
Low metabolic reserve  hypoxia and late decelerations

32. • Results :
1. Negative result ( Reassuring ) :  repeat weekly or when
indicated
2. Positive result
If mature  termination of pregnancy
If ˂ 32 weeks  biophysical profile
3. Equivocal : When stimulation associated with
decelerations cannot be interpreted  repeat next day or
do biophysical profile

33. • Advantages
Early warning test for fetal hypoxia with low false negative
value 1/1000
• Disadvantages :
1. High false positive value 25-75 % (although less than NST )
2. Has many contraindications
I. Patients with potential weak scar
II. Predispose to preterm labour
III. History of antepartum haemorrhage
IV. Placenta previa
V. Incompetent cervix
VI. Multiple gestation