Comprehensive prenatal care often includes a CTG. But what kind of device are you actually connected to, and how does it work? Why is it so important, and what do the curves recorded by the CTG show? In this article, we’ve summarized and answered the most important questions about this examination for you.

What is an CTG?

The abbreviation CTG stands for cardiotocogram / Kardiotokogram. With the help of a CTG, your midwife or your gynecologist/obstetrician measures your contractions and your baby’s heartbeat. This is done using two different sensors attached to your abdomen with straps: an ultrasound sensor that measures your baby’s heart rate using ultrasound signals (the cardiograph), and a pressure sensor (the tocograph) that detects changes in abdominal circumference and, in turn, the strength and frequency of contractions, if any are present. By measuring the heartbeat, the CTG also allows an assessment of your baby’s oxygen supply. The examination is painless and safe for both mother and baby.

When is a CTG performed?

If your pregnancy proceeds without complications, your gynecologist usually performs only the three mandated examinations. Since last year, a reorganization of statutory prenatal care has stated that, in uncomplicated pregnancies, no further CTGs are required during check-ups until the due date. According to the new guidelines, a CTG is only necessary in the following cases:

• If a premature birth is imminent before the 28th week of pregnancy

• In case of premature labor or suspicion thereof

• During bleeding

• In case of abnormalities in Doppler ultrasound (special ultrasound examination of the vascular supply)

• In multiple pregnancies

• In case of too much or too little amniotic fluid

• Suspected placental insufficiency

• When taking labor suppressants

• In the event of past miscarriages

• In case of overdue pregnancy (from the 40th week of pregnancy )

Technically, a CTG is possible from about the . Shortly before and during the , the CTG becomes important for every pregnant woman: Usually, you will be connected to the CTG immediately upon arrival at the delivery hospital to monitor contractions and your baby’s well-being. (During labor, a CTG is performed approximately every two hours.)

How does a CTG examination proceed?

During the CTG, you sit or lie in a quiet room. One or two belts are placed around your abdomen, with the CTG sensors attached to them. These are connected to a monitor via a cable. One sensor, the tocograph, responds to the changing tension of your abdominal wall caused by pressure changes in your uterus, thereby measuring contraction activity. The other sensor, the cardiograph, sends ultrasound signals through your abdomen, which are then reflected by your baby’s heart. It records the time between two heartbeats and calculates the number of heartbeats per minute, i.e., your baby’s heart rate.

Why is a CTG examination important?

A CTG allows complications during pregnancy to be detected early. If the CTG values deviate from the normal range, this may indicate restricted or poor blood flow to the baby or a threatened preterm birth. (During delivery, the CTG can also indicate umbilical cord blood or oxygen deprivation, or a nuchal cord with the .) The earlier these complications are identified, the better your doctor can intervene and provide the best possible help for you and your baby.

What do the CTG values/-curves mean?

During the CTG, two or four values are recorded on a long paper strip. In our image, you see the version with two values. The upper curve represents the baby’s heart rate. Normally, values between 120 and 160 beats per minute are observed here. However, there can also be completely harmless deviations, for example, if your baby is moving a lot or sleeping. During labor, this curve can also be used to see how your baby reacts to the . When the uterus contracts during a contraction, less blood reaches the baby, and the heartbeat slows down for a short moment. After the contraction, the heartbeat normalizes again.

The lower curve in the example image shows the contractions. The strong fluctuations of the line each represent a contraction; the curve depicts the duration and frequency of the contractions. It’s possible for the CTG to record contractions that you don’t feel at all, because the sensor is very sensitive. The recording of contractions is also called the toco value.

Modern CTG devices can also record fetal movements, which would otherwise only be visible on ultrasound. This third value then appears as small, vertical lines on the paper strip. Your doctor may also ask you to press a button or let them know when you feel your baby’s movements yourself. This is the fourth value and is also marked with small, vertical lines.

The FIGO score

Your doctor will then evaluate the CTG values using the so-called FIGO score. Your baby’s heart rate is assessed using the following four criteria:

• Base frequency: How many heartbeats per minute were recorded?

• Bandwidth: Does the heart rate fluctuate?

• Deceleration: Does the heart rate slow down regularly?

• Acceleration: Does the heart rate regularly increase?

These criteria are evaluated individually and then considered in the context of the overall course of pregnancy and childbirth. This allows for a quick and accurate assessment of the baby’s condition, which additional examinations are necessary, and when prompt intervention is needed.

In any case, your doctor will talk to you about everything and explain the next steps. Be sure to ask any questions that come up. This can help ease many worries. The CTG helps monitor your pregnancy and ensure that your baby is doing well. It can also reassure you and give you the chance to discuss any emerging concerns directly with your doctor. The goal is to make this period of pregnancy as pleasant and beautiful as possible for you and your baby.