Monitoring of heart sounds and contractions


A contraceptive pen is a technical procedure that can record both fetal heart activity and the activity of contractions in pregnant women. The term cardiotocography (CTG for short) is also used synonymously, which is derived from the Greek word tokos (= contractions). This method is used on the one hand as part of preventive examinations during pregnancy and on the other hand to monitor the birth process.

The heart activity of the unborn child is measured by Doppler ultrasound and recorded as heart rate. The unit of measurement is beats per minute. The mother’s contractions are measured by means of a pressure sensor which registers the change in abdominal circumference during a contraction.

However, depending on the physical constitution of the pregnant woman, the pressure measurement may vary under certain circumstances and not provide very accurate values. Therefore, in addition to the actual measurement, the subjective feeling about the perception of the contractions by the pregnant woman is also important. It is best for the expectant mother to lie on her side or on her back for the duration of the examination.

Two straps are usually placed around her abdomen to hold the respective measuring sensors on the abdominal wall. Usually the sensors are connected to the actual device for recording via a cable. There, the measured data can be printed on paper strips.

With modern devices, data transmission is also possible via radio, so that the woman can move freely during the examination. The contraction recorder is primarily used to monitor the child’s heartbeat. These correlate directly with the oxygen supply of the unborn child, which is indispensable for the physical development.

If, for example, the heart rate drops, this is to be interpreted as a direct sign of a reduced oxygen supply and should be corrected as quickly as possible in order not to endanger the health of the unborn child. Usually this examination is only carried out from the 30th week of pregnancy onwards. It is usually repeated every 14 days as part of the usual preventive medical check-ups if there are no further abnormalities.

However, in the case of certain risk constellations or complications during pregnancy, it may be advisable to have a CTG examination earlier or at shorter intervals. According to maternity guidelines, a prenatal CTG examination is only indicated if a premature birth is expected or other risk constellations exist. As a standard, however, this examination should be performed during childbirth in all women.