What is CTG ?

• Continuous registration of fetal heart action, recording of uterine motility and fetal movements
• Standard for the diagnosis  of fetal hypoxia, possibly disorders of uterine activity

Tocography = continuous recording of uterine activity

• External registration
  • sensor attached with an elastic belt to the abdomen in the area of the uterine fundus
  • responds to changes in abdominal wall tension during contraction 
  •  the quality of the recording depends on the thickness of the abdominal wall
  • norm: 6 – 8 contractions / 10 minutes

• Internal registration
  • using a water-filled catheter inserted into the uterine cavity after the amniotic fluid has drained
  •  measurement of intrauterine pressure changes
  •  limited indications (significant maternal obesity, pathological positions of the fetus, previous caesarean section, hypertonic contractions, protracted course of labour) due to the risk of injury to the placenta, myometrium and entry of infection

Cardiography

 = continuous recording of fetal heart action, method of early detection of fetal hypoxia

Methods of registration:

1. Phonocardiography – historical significance only
2. Doppler ultrasound cardiography 
   1. captures the movement of the heart wall or valves 
   2. the ultrasound head is attached to the abdomen, maximum fetal heart sounds are in the area of the punctum
3. ECG (indirectly – electrodes on the mother's abdominal wall,  directly – spiral electrode into the skin of the fetal head)

The ST segment expresses changes in the ability of the myocardium to respond to hypoxia

• ST elevation - response of the myocardium to hypoxia by the supply of catecholamines, activation of beta receptors and glycolysis in the myocardium.
• ST depression – the myocardium cannot respond to stress and hypoxia.
• ST depression for more than 10 min = always pathological CTG and pH < 7.1
• CTG and STAN will reduce the occurrence of metabolic acidosis by 60% and the number of operations for fetal distress by 25%.

FPO, resp. fSpO2

Principle: light with a wavelength of 660 mm and 920 mm penetrates the tissue. 

• reduced hemoglobin and oxidized hemoglobin absorb differently
• O2  saturation in % (SpO2 ) can be calculated from thE difference in absorption
• SpO2 must not fall below 30% / 10 min. (hypoxia in 50%)
• Saturation < 10% is definitely hypoxia.
• FPO can reduce the number of cesarean sections.

Cardiography - evaluation

1. basal frequency
2. variability (oscillation)
3. accelerations and decelerations 

Basal frequency 

• Average frequency during a period of at least 10 minutes outside of uterine contractions
• Norm (at term delivery) – 110–150/min
• Tachycardia – up to 170/min
• Severe tachycardia – over 170/min
• Bradycardia – below 110/min
• Severe bradycardia – below 100/min

Variability 

• Range of changes in frequency that cannot be evaluated as acceleration or deceleration
• Dependence on fetal sleep or waking
• Loss of variability is an important sign of fetal hypoxia
• It reflects increased sympathetic tone
• Norm: 10 – 25 beats/ min…undulatory curve (awake fetal state)
• Above 25 beats/min…saltatorial curve (umbilical cord compression)
• 5-10 beats/min…narrow undulatory curve (fetal sleep)
• Less than 5/min…silent curve (hypoxia or drug-induced fetal central depression)

Accelerations and decelerations

• Short-term frequency changes

1. Acceleration – an increase in heart rate by 15 beats/min lasting about 10-15 seconds, usually caused by fetal movements (physiological state, indicating good oxygenation of the fetus)
2. Deceleration – decrease in heart rate by 15 beats/min lasting about 10-15 seconds (isolated or in connection with uterine contractions) 

Evaluation of fetal movements 


The norm is at least 2 movements in 20 minutes.

Use of CTG

1. Antepartum
   1. in the form of non-stress test, possibly stress-test (oxytocin stress test, nipple stimulation, step-test)
2. Initial
   1. part of the initial examination of the mother before giving birth
3. Intrapartum
   1. during childbirth

CTG monitor


Monitoring: fHR (ultrasound probe), TOCO also monitoring of multiple pregnancies (more ultrasound probes)

Option to monitor the mother's vital signs:

• ECG
• NIBP
• SpO2

Conclusion 

• Changes in the CTG must always be evaluated together with the overall clinical situation
• It is not permissible to conclude that the fetus is at risk only on the basis of some sections of the CTG record