Labor pen (CTG) | Babies |

Labor pen (CTG)

What is a labor writer?

The labor writer, also known as a cardiotocograph (CTG) or cardiac tachograph, is a medical device that allows the doctor or midwife to measure the unborn baby's heart rate in relation to the length, strength and frequency of the mother's contractions. It is used primarily in clinics during childbirth to continuously monitor the baby's health. Under certain circumstances, the labor clerk is also used during pregnancy.

When do I need a CTG in pregnancy?

According to the maternity guidelines of the Federal Committee of Physicians and Health Insurance Funds, the CTG is not routinely used in pregnancy. It can be used especially for high-risk pregnancies. Reasons for one or more examinations with a CTG device may be (Maternity Guidelines 2003):

  • Certain pre-existing conditions of the mother such as anemia, diabetes or hypertension
  • Suspected impending miscarriage from week 25 of pregnancy
  • Miscarriage or stillbirth in a previous pregnancy
  • Suspected preterm labor from week 27 of pregnancy
  • The heart sounds of the child are too slow, too fast or short
  • Multiple pregnancy
  • Suspected placental insufficiency (the child is not sufficiently supplied by the mother cake)
  • vaginal bleeding
  • Suspected transfer (the ET is exceeded by more than a week)
  • Control of anti-buzzing drugs
  • Suspected developmental delays in the baby

How does a CTG device work?

You can sit on a chair or lie on its side while lying on a lounger. Then you get an elastic waist belt folded. This may be a bit tight - say in this case. Nevertheless, your freedom of movement will be very limited, and you should sit or lie very still during the recording. The abdominal belt attaches a transducer to record the heart rate and a pressure transducer to record any contractions. They are connected with cables to a monitor: one transducer is rubbed with gel and captures the heart sounds of your baby, the second transducer registers the tension of the abdominal wall and thus possible contractions. There are also transducers that can also register the child's movements, then you get a so-called K-CTG (Kineto-Kardiotokogramm).

At the Fulda Hospital, a quadontocograph has been developed over the past few years, making it possible to measure not only two but four abdominal sites. This makes the measurements more accurate. This device is not (yet) very widespread (Werner 2000).
You will be connected to the device for 20 to 30 minutes, after which the doctor or midwife will evaluate the result. So, allow enough time for the investigation and take something to read.

The normal heart rate of a baby during pregnancy is between 110 and 150 beats per minute, depending on the SSW. Recent studies show that the heart rate increases to 115 to 160 beats per minute at the time of delivery. Their labor activity is assessed in terms of strength, duration and regularity (DGGG 2008).

How safe is a CTG and are there risks?

Like the ultrasound device and the Doppler sonography, the cardiotocograph works with ultrasound waves, except that the CTG does not produce an image. Instead, the low-frequency sound waves are converted into sounds and transmitted as curves on a sheet. Studies have so far failed to demonstrate any negative impact of sound waves on the mother or child. Nevertheless one should not make a CTG longer and more often than necessary (DGGG 2008).

Evaluating the curves is not easy. You have to be trained in it and consider different influencing factors. For example, it depends on whether the fetus was currently in a waking, sleeping or REM phase during the examination. Like an adult, it has a big impact on the heart activity. Also, what drugs the mother takes, a cold with fever or the posture during the recording can influence the examination result. Therefore, labor clerks provide only a snapshot and not infrequently turns out to be a disturbing result as a false alarm. Additional examinations such as an ultrasound scan can bring clarity.

However, a CTG can be very reliable in a possible transmission of the baby indicate a lack of oxygen supply threatens.


Cardiotocography (CTG). Lecture notes Main lecture WS 2001 (Source: JENSEN u.MARTIUS in: Proposal and Perinatology, Thieme, Chapter 16, pp. 386-442

Maternity guidelines. 2003. "Guidelines of the Federal Committee for Doctors and Health Insurance Funds on medical care in pregnancy and after delivery (" Maternity Guidelines ") in the version of 10.12.1985, last amended on 24.12.2003., Entered into force on 12.7.2003
The Maternity Guidelines as pdf for download at the Joint Federal Committee [as of January 2008]

DGGG 2008. German Society for Gynecology and Obstetrics (DGGG). Working Group of the German Society for Perinatal Medicine (DGPM) and the AGM for Materno-Fetal Medicine (AGMFM): "Application of the CTG during Pregnancy and Childbirth", AWMF Guidelines Register No. 015/036
The document at the University of Düsseldorf [as of January 2008]

Werner 2000. Prof. dr. Martin Werner, Dipl.-Ing. (FH) Bernd Heil "Importance of Four Channel Ethography in Diagnosis and its Realization in the Clinic", 2000, University of Applied Sciences Fulda
The document as PDf at FH Fulda [as of January 2008]

Höfer, Silvia; Száz, Nora: "Midwife knowledge". Gräfe und Unzer, Munich 2006. 2nd edition 2007.

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