Cardiotocography

In the Cardiotocography Using an ultrasound tansducer and a pressure sensor, a tokograph records the heartbeat of an unborn child as a function of the labor activity of the expectant mother, which is primarily intended to ensure the child's health during the birth.

The data measured in this way are presented in a cardiotocogram and, after evaluating them using schemes such as the Fischer scores, are used by the obstetricians to assess the potential need for a caesarean section. In some cases, cardiotocographs also take place during pregnancy, but are only recommended outside of the birth in exceptional cases, as they often trigger false alarms and could induce the doctor to initiate the birth unnecessarily early.

What is cardiotocography?

Cardiotocography is a gynecological control procedure that can map the heartbeat of the unborn child in relation to the labor activity of the expectant mother. Konrad Hammacher is considered to be the inventor of the procedure, which is now one of the standard procedures in the field of pregnancy monitoring during an ongoing birth.

As a rule, cardiotocography is an external, i.e. non-invasive, procedure and takes measurements over the mother's abdominal wall. An ultrasound transducer and a pressure sensor work together in cardiotocography. They send a sound into the womb that reaches the child's heart and returns an echo that is used to calculate the heart rate. The tokograph outputs the measurement data in the form of a cardiotocogram, which the obstetricians can identify any complications or problems during the birth early enough and then rectify them.

Function, effect & goals

Cardiotocography is primarily performed during the first 30 minutes of childbirth to ensure the health of the unborn child. If there are no abnormalities in the cardiotocogram in the first 30 minutes, the obstetricians usually switch off the device and only record the values ​​continuously again during the late opening phase. The measuring sensors of an ultrasonic transducer and a pressure sensor are attached to the expectant mother's belly to carry out the measuring process.

The ultrasonic transducer lies under an abdominal bandage, where it remains mobile and can thus be adapted to the position of the unborn child. The transducer finally sends sound waves into the womb, which reach the heart of the unborn child and trigger an echo there. The reflected echo is registered by the receiver of the tansducer and is used to calculate the heart rate. Modern ultrasonic transducers are also able to register child movements.

Since the heart rate of the fetus is to be shown in the cardiotocography as a function of the contractions, the pressure sensor measures the contractions of the uterine muscles at the same time.

The device derives these values ​​from the expectant mother's abdominal wall tension and records the data calculated in this way. The fetal heart rate sometimes drops sharply as a result of a lack of oxygen. Such so-called decelerations can be documented using cardiotocography and may require a caesarean section. In particular, late decelerations following each contraction are an indication of a risk to the fetus. Early decelerations that are synchronous with labor, on the other hand, are usually harmless as long as they have existed since the beginning of the birth and do not suddenly appear towards the end.

In order to evaluate the measurement data of the cardiotocography, schemes such as the evaluation in Fischer scores are used. In the near future, the evaluation should be largely computer-controlled according to recognized guidelines.

Risks, side effects & dangers

In addition to using it during childbirth, doctors sometimes also recommend cardiotocography in late pregnancy. In particular, this can happen in high-risk pregnancies. However, many experts advise against cardiotocography during pregnancy, as the procedure has resulted in complications in the past. For example, cardiotocography can trigger a false alarm and unreasonably induce the doctor to initiate a birth.

If cardiotocography is sometimes used during pregnancy on diabetes patients or women suffering from high blood pressure in order to monitor possible risks, an experienced and competent doctor is essential to assess the cardiototogram. Any abnormal findings should always be clarified through further examinations before the doctor initiates any measures. Abnormalities are often due to normal processes such as movements of the fetus.

Cardiotocography is, however, rightly used during pregnancy if the heart rate is disturbed in advance or if there is a risk of premature birth. At birth itself, the measurement is ultimately standard and is not associated with increased risks or side effects for either the mother or the unborn child. On the whole, the procedure is completely painless for the mother, but the unborn child should not be irradiated with sound energy for an unnecessarily long time during the birth.

When interpreting the recorded data, the obstetricians must always include the mother's constitution and her information on labor activity, since the tokograph records, for example, minor labor activity with high rashes in the case of severe changes in the abdominal circumference of a very slim pregnant woman. In conclusion, an obese pregnant woman may lack rashes, even though the labor activity has long exceeded the norm.