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CTG Test During Pregnancy: Why Is It Done & Normal Range


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CTG is a noninvasive ultrasound test that measures the fetal heart rate. The test is done with an electronic transducer, which is placed on the fetal scalp from over the belly.

The test also determines the baseline rate or the fetal heart rate within a 10-minute window without accelerations or decelerations.

A CTG test is performed to measure fetal heart rate during pregnancy. The results of the test can be used to monitor the baby’s development.

High-risk pregnancies may require continuous monitoring. In these cases, the risk of complications can increase during the labour process, such as green amniotic fluid, fever, and excessive bleeding.

In addition to monitoring the fetal heart rate, a CTG can also show how strong contractions are.

If you want to know more about CTG during pregnancy, why it’s done, and its normal range, continue reading and get answers to your doubts.

What Is CTG Test In Pregnancy?

CTG stands for Cardiotocography. It is a type of test done to measure the heart rate of the fetus during pregnancy. This test is used to determine if the baby’s heart rate is normal or if there is fetal distress. The process involves the use of a special machine called a cardiotocograph.

During pregnancy, abnormal CTG levels are associated with poor fetal outcomes. Specifically, abnormal CTG levels in high-risk pregnancies have been linked to higher rates of fetal morbidity and mortality. Originally, CTG was used to detect early changes in fetal heart rate associated with the presence of hypoxia.

The CTG test uses sound waves to monitor the heart rate of the baby. These sound waves are sent through a special machine to a monitor to determine the heart rate of the baby. The monitor can also measure the frequency of contractions and heartbeat.

CTG test is used before and during labour to monitor the fetal heart rate. This type of test is most commonly performed external tests, with the equipment placed on the mother’s abdomen.

It involves two different sets of transducers – one for the mother and one for the baby. The ultrasound on one plate measures the baby’s heart rate, while the other plate measures pressure on the abdomen to measure contractions.

The CTG test is most commonly used during the third trimester of pregnancy, at about 28 weeks. However, local guidelines differ from people to people and need to need in reference to the gestational age at which the test should be conducted.

How Does Cardiotocography Work?

Cardiotocography is a diagnostic tool that measures the heart rate of the fetus. It is used to monitor the heart rate of the baby during pregnancy and labour. It uses ultrasound to measure the rate of heartbeat.

The ultrasound waves travel freely through the fluids and soft tissues of the womb, then bounce back as echoes when they encounter solid objects, such as a heart chamber or a valve. The echoes of different structures are reflected differently and are therefore used to assess different aspects of the baby’s heart anf identify defects if any.

The machine used to obtain the data is commonly referred to as a “foetal monitor.” During the test, ultrasound transducers are placed against the abdomen of the mother. These transducers record fetal heartbeat and uterine activity to determine whether a baby is getting enough oxygen. The procedure is performed during the ante and postpartum periods of pregnancy.

Why Is CTG Test Done During Pregnancy? 

CTG for pregnancy can detect several different problems, including if the baby is small or not growing properly. It can also detect problems with the placenta. It can also tell whether the baby is getting too much or too little amniotic fluid. A CTG test is done to check all these things.

  • To Check If Baby Is Small or Not Growing Properly

Cardiotocography is a test that monitors the baby’s heart rate. Normally, the heart rate of a baby ranges from 110 to 160 beats per minute, and it increases when the baby is moving. This test is done to check if the baby is small or if they are not going properly.

  • If There Is Too Much or Too Little Amniotic Fluid

Cardiotocography is used to determine if there is too much or too little amniotic fluid in a pregnant woman’s womb. Many health conditions can affect how much fluid a woman’s womb contains. Pregnant women with low amniotic fluid are at high risk of premature birth and postpartum haemorrhage.

  • To Check If Baby’s Movements Have Slowed Down

Movement is a key indicator of your baby’s health, and if you notice a change in pattern, you should consult your healthcare provider. A CTG test is done to check if the baby’s movements have slowed down.

  • To Check If There Is A Problem With Placenta

If you suspect that there might be a problem with your placenta, it is essential to get an immediate medical diagnosis. The placenta is a fleshy, blood-filled organ that develops with your baby during pregnancy. A CTG test can help to know if there is a problem with the placenta.

  • If You Have Diabetes

Cardiotocography is a diagnostic test used to measure heart rate. It can be an important tool if you have diabetes. Using this test can help doctors determine whether your diabetes is affecting your heart.

  • If You Are Carrying Twins

If you are carrying twins, you may be offered a Cardiotocography scan to assess the condition of your heart rate. This test is performed by sending sound waves through the womb to the baby’s heart.

  • If You Are Past Your Due Date

If you are past your due date, your doctor may want to check the heart rate of the baby through Cardiotocography. This test is done by listening to the baby’s heartbeat with a machine that records it and produces a printout.

  • If You Have Third-Trimester Amniocentesis

Third-trimester amniocentesis is a diagnostic procedure used to look at the heart and lung development of your unborn child. It is not required in all cases and is typically only done in the last 15 weeks of pregnancy.

  • If You Have Previously Lost a Baby

If you have previously lost a baby during the second half of the pregnancy due to reasons unknown, a CTG test is necessary. It will help to determine if it will happen again.

  • Baby Diagnosed with Birth Defect or Abnormality

If your baby is diagnosed with an abnormality or birth defect, a CTG test scan will be required to monitor their condition from time to time.

What Is CTG Test In Pregnancy Normal Range?

A CTG test is a diagnostic test during pregnancy that detects abnormalities in the baby’s heart rate. The average heart rate of a baby is 110-160 beats per minute. A heart rate over or below this range is indicative of health problems.

The test results are interpreted as, Reassuring (Normal Range), Suspicious or Abnormal. During this test, five components, i.e. body movements, breathing movements, muscle tone, amniotic fluid, and heartbeat, are given scores from 0 to 2. These scores are added to check the result.

A score of 8 to 10 shows the normal range of CTG tests during pregnancy. A score of 6 is considered borderline, and below 6 is worrisome. Here is the normal range of CTG tests during pregnancy.

  • Baseline Heart Rate

The Baseline Heart Rate of the CTG test during pregnancy is a measure of the fetal heart rate. This measure is highly predictive of fetal oxygenation. A normal rate is between 110 and 160 beats per minute.

  • Baseline Variability

Baseline variability of CTG tests during pregnancy is a key consideration in fetal monitoring. If the CTG is high, it may be indicative of fetal decompensation. The normal range of baseline variability is 5 to 25 bpm.

  • Decelerations

CTG during pregnancy is a non-stress test that measures the fetal heart rate (HR). It is used to determine whether fetal movements are causing an increase in fetal HR. The Decelerations of the test should be “None or early” and “Variable decelerations with no concerning characteristics for less than 90 minutes”.


  • What Does a CTG Scan Show?

CTG scans measure the heart rate during pregnancy. CTG scan pregnancy shows whether the baby is getting enough oxygen or not. The scan can also reveal how much the uterus is contracting.

  • What Does Abnormal CTG Mean?

A woman’s CTG is very important during pregnancy. When this test comes back with an abnormal reading, it can indicate a problem. Abnormal CTGs may signal a problem with the baby’s heart or placenta and will need further investigation and potential intervention.

  • What Is A Normal Fetal Heart Rate?

fetal heart rate of 110 to 160 beats per minute is considered normal. A baby’s heart rate that exceeds that may be a sign of fetal heart failure.


Cardiotocography or  CTG for pregnancy, is a technique used to monitor a fetus’s heartbeat and contractions. The process involves the use of a special machine called a cardiotocograph. This machine uses a special light to detect contractions and the fetal heartbeat. The procedure is noninvasive and mostly done during the third trimester or labour. It helps to continuously monitor your baby’s heartbeat. If the test shows that your baby’s heart rate is decreasing, an emergency caesarean might be required.


Srujana Mohanty
She is the Managing Editor of Cogito137, one of India’s leading student-run science communication magazines. She's been working in scientific and medical writing and editing since 2018, also associated with the quality assurance team of scientific journal editing. Majored in Chemistry with a minor in Biology at IISER Kolkata, Srujana loves doodling and watching series.


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