Cardiotocography (CTG)

Cardiotocography (CTG) - Overview

Cardiotocography (CTG) is a medical test that is used to monitor fetal well-being during pregnancy and childbirth. The test records the fetal heart rate and uterine contractions, and it is often performed in the third trimester of pregnancy or during labor. The results of the CTG can help healthcare providers determine whether the fetus is getting enough oxygen and whether intervention is necessary.

Cardiotocography (CTG) Procedure

A cardiotocography (CTG) is a non-invasive test that monitors the fetal heart rate and uterine contractions during pregnancy. It is usually performed in the third trimester, but can also be done earlier if necessary. 

Here's how the CTG is performed:

1.) The mother will lie down on an examination table with her abdomen exposed.

2.) Two sensors will be attached to her abdomen: one to measure the fetal heart rate, and the other to measure uterine contractions. The sensors are attached with elastic belts, similar to those used during an ultrasound.

3.) The fetal heart rate sensor uses ultrasound technology to detect the baby's heart rate. The sensor is placed over the baby's back or chest, depending on the baby's position.

4.) The uterine contraction sensor uses a pressure-sensitive pad to detect contractions. The sensor is placed over the uterus, typically near the top of the mother's uterus.

5.) The sensors are connected to a machine that records the fetal heart rate and uterine contractions. The machine produces a graph called a "trace," which shows the changes in fetal heart rate and uterine contractions over time.

6.) The CTG is usually performed for about 20-30 minutes, although it can be done for longer if necessary.

During the CTG, the mother may be asked to press a button on the machine when she feels the baby move so that any changes in fetal heart rate can be correlated with the baby's movements. The CTG is typically performed in the hospital or doctor's office and can be done as an outpatient procedure.

Overall, the CTG is a safe and non-invasive test that provides important information about the fetal heart rate and uterine contractions during pregnancy.

What Parameters are measured by Cardiotocography (CTG)?

The CTG (Cardiotocogram) measures two main parameters: the fetal heart rate (FHR) and uterine contractions.

The fetal heart rate is the number of times the fetal heart beats per minute. The CTG records the FHR by placing a sensor on the mother's abdomen over the fetal heart. The FHR can provide important information about fetal well-being, as changes in the heart rate can indicate whether the fetus is getting enough oxygen.

The uterine contractions are the muscle contractions of the uterus that occur during labor. The CTG records the uterine contractions by placing a second sensor on the mother's abdomen over the uterus. The contractions are measured in terms of frequency, duration, and strength.

The CTG graphically displays these parameters over time. The FHR is plotted on the vertical axis, and the uterine contractions are plotted on the horizontal axis. The graph allows healthcare providers to see how the fetal heart rate responds to uterine contractions and whether the fetus is getting enough oxygen.

The CTG can also be used to monitor fetal well-being during labor. During this time, the test can provide information about the fetal heart rate response to contractions and the effectiveness of interventions such as medications or amniotomy (rupture of the amniotic sac). A non-reactive CTG during labor may indicate that an emergency cesarean section is necessary.

How is Cardiotocography (CTG) Interpreted?

A CTG (Cardiotocogram) is a graph that displays the fetal heart rate (FHR) and uterine contractions over time. In a normal CTG, the FHR should increase in response to uterine contractions and then return to its baseline level once the contraction is over. This is known as a reactive CTG. A reactive CTG is a reassuring sign that the fetus is receiving adequate oxygen and is not under any stress.

When the FHR increases in response to a uterine contraction, it is called acceleration. This is a normal response and indicates that the fetus is getting enough oxygen. The acceleration should be at least 15 beats per minute (bpm) above the baseline FHR and should last for at least 15 seconds. The baseline FHR is the average heart rate over a 10-minute period, excluding accelerations and decelerations. Additionally, there should be no decelerations in the fetal heart rate that last longer than 10 seconds or drop below a certain threshold.

If the FHR does not increase in response to uterine contractions, the CTG is considered non-reactive. This may indicate that the fetus is not getting enough oxygen, and further testing or intervention may be necessary.

A non-reactive CTG may show a variety of patterns, including:

1.) Flatline: This means that the FHR is not changing and may indicate fetal distress.

2.) Variable decelerations: This means that the FHR is decreasing and then returning to baseline, often in a jagged pattern. This may indicate that the fetus is experiencing cord compression, which can limit oxygen flow.

3.) Late decelerations: This means that the FHR is decreasing after the start of a uterine contraction and returning to baseline after the contraction is over. This may indicate that the fetus is not getting enough oxygen due to uteroplacental insufficiency, which can occur when the placenta is not functioning properly.

If a non-reactive CTG is observed, further testing or intervention may be necessary to ensure fetal well-being. This may include additional monitoring, such as a biophysical profile or a fetal scalp electrode, or intervention, such as amniotomy (rupture of the amniotic sac) or delivery by cesarean section.

While the CTG is a valuable tool for monitoring fetal well-being, it is not a perfect test. Some CTGs may be falsely non-reactive, leading to unnecessary interventions or cesarean sections. In addition, some CTGs may be falsely reactive, leading to unnecessary monitoring or interventions.

Overall, the CTG is an important tool for monitoring fetal well-being during pregnancy and childbirth. The test can provide valuable information about the fetal heart rate response to uterine contractions and can help healthcare providers determine whether intervention is necessary. However, it is important to interpret the results of the CTG in the context of other clinical factors and to avoid unnecessary interventions based solely on the results of the test.