Cardiotocography

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Typical CTG without labor
A: Fetal heart activity
B : Fetal movements felt by the mother (recorded by pressing a button)
C: Fetal movements
D: Uterine contractions

Cardiotocography or -graphy (English C ardio t oco g raphy ; CTG ; Herztonwehenschreibung ) refers to a method for the simultaneous (concurrent) registering and recording the heart rate of the fetus and the uterine contractions (Greek tokos ) at the expectant mother. The procedure is used both in pregnancy care and for monitoring during childbirth.

Technology and evaluation

The heart rate of the fetus is usually with the wave Pulsed Doppler determined -Ultrasound and in min -1 or bpm ( English beats per minute recorded). The mother's labor activity is measured with a separate labor sensor, a pressure gauge and also recorded. There are two methods for this: the rarely used intrauterine, direct pressure measurement, which can only be used after opening the amniotic sac, i.e. during childbirth, and the external pressure measurement using a tocodynamometer, which is common today. This differential pressure meter reacts to the change in abdominal tension during a contraction, which is why there are large individual fluctuations in the recording of contractions: The "hardness" of the belly of a very slim pregnant woman (with very little subcutaneous fat tissue) changes much more clearly than that of one larger pregnant women. The bandwidth of the recording differences ranges from large deflections of the tokograph with slight contractions of a slim pregnant woman to completely absent deflections during the labor pains of an obese woman in loss. When interpreting a CTG or calibrating the device, the constitution of the pregnant woman and her information about the perceptibility of contractions must therefore also be taken into account.

The course of the changes in the child's heart rate is interpreted taking into account the labor activity and the gestational age (in the case of pregnant women) or the progress of the birth since then. If there is a suspicion of insufficient care for the child ( uteroplacental dysfunction ), a labor stress test with CTG control can be carried out. However, it has many false-positive results.

During childbirth, a lack of oxygen can, among other things, lead to a temporary decrease in the fetal heart rate (FHR), a so-called deceleration . Particularly “late” decelerations that occur after a contraction can indicate that the child is at risk. "Early" decelerations that occur synchronously with the contractions are less likely to be signs of acute danger, but if they occur regularly at the beginning of labor, they can be the reason for obstetric intervention. If the FHR remains below 120 bpm for more than three minutes, it is said to be mild bradycardia and below 100 bpm as severe bradycardia . Bradycardia when the head enters the pelvis is also called the entry effect.

The evaluation of the CTG can be based on various schemes, e.g. B. be done using the Fischer score . Guidelines for evaluating the CTG are also issued by the Fédération Internationale de Gynécologie et d'Obstétrique (FIGO) and other national and international bodies. The introduction of computerized documentation and evaluation systems is the focus of current research programs.

The previous sentence of February 16, 2010 needs to be revised: Such devices are already in use and are recommended ("Oxford-CTG").
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history

A cardiotocograph recording contractions and heart rate. The inductive (contactless) charger with trays for 3 wireless sensors is on the device

Obstetric surveillance procedures were first reported in the early 18th century. The focus was on the proof that an unborn child is (still) alive. Auscultation of fetal heart sounds has been widespread since the first decades of the 19th century . Since the mid-19th century, more attention has been paid to the fetal heart rate (FHR) and its changes during labor. However, continuous recording was only possible as a result of technical developments at the beginning of the 20th century. First, the fetal heart rate was determined by phonocardiography , i.e. by deriving the heart sound with a microphone. Other attempts consisted in deriving the child's electrocardiogram in different ways and determining the heart rate from it.

The ultrasonic Doppler method has been used since the late 1960s. In this case, ultrasound sent from a placed on the belly of the mother probe, reflected by the fetal heart and received again. The child's heart rate is determined using the Doppler effect (frequency deviation of the received signal due to the movement of the reflecting heart). In connection with the simultaneous registration of labor activity, phonocardiotocography, ultrasonocardiotocography and fetal electrocardiotocography are possible today.

The uterine activity measurement goes back to the description of a tocodynamometer in 1957, which has a fixed outer ring and a movable detector plate in between, the "indentation force" of which is determined by means of strain gauges. The principle has been modified many times in order to compensate for interference.

Today (2015) the CTG devices (Kineto-CTG) commonly used in the delivery room record not only fetal heart rate and maternal labor, but also child movements (movement = Greek kinesis ). These also provide information about the child's condition. The child's movements can be detected using the same ultrasonic sensor that measures the heart's activity. With these devices, the data are usually transmitted wirelessly from battery-operated converters on the mother's abdominal wall to the recording unit. This allows the woman to move freely while monitoring the child's condition. The photo opposite shows such a CTG.

Individual evidence

  1. ↑ Dirk Borgwardt: My pregnancy companion. Safe through pregnancy: appointments - examinations . 1st edition. Trias Verlag , Stuttgart 2008, ISBN 978-3-8304-3714-7 , section The CTG - The Heart Sound-Wehenkurve , p. 88 ( limited preview in Google Book Search - PDF edition).
  2. ↑ Use of the CTG during pregnancy and childbirth. (PDF; 267 KB) In: AWMF online - guidelines. German Society for Gynecology and Obstetrics , working group of the German Society for Perinatal Medicine (DGPM) and the AG for Materno-Fetal Medicine (AGMFM), August 2013, p. 10 , archived from the original on May 17, 2018 ; accessed on October 7, 2019 (registration number 015/036, section 6.1.2 contractions test (stress test) ).
  3. ↑ Wolfgang Künzel : Beginnings of the cardiotocography. In: The gynecologist . Volume 42, No. 5, 2009, pp. 328-335, pp. 328-335, doi : 10.1007 / s00129-008-2285-7 .
  4. ↑ Gabriele Kaschner: Investigations on the quality of the fetal heart rate registration: Comparison of antepartal registrations from 1972 and 1998 . Dissertation. Heinrich Heine University Düsseldorf - Medical Faculty, 2003, Section 1.1 Development of Cardiotocography , p. 1 f ., urn : nbn: de: hbz: 061-20040505-000813-4 ( full text at DNB [PDF; 396 kB ]).
  5. ↑ CN Smyth: The Guard Ring Tocodynamometer. In: The journal of obstetrics and gynecology of the British Empire. Volume 64, No. 1, 1957, pp. 59-66, doi : 10.1111 / j.1471-0528.1957.tb02599.x .

literature

Web links

Commons : Cardiotocographs  - collection of images, videos, and audio files