What is a Fetal Growth Scan?

The growth scan, sometimes called the wellbeing scan, or positioning scan, occurs when the mother is between 23 and 40 weeks pregnant. It checks how well the baby is growing and the uterus (womb) position.

 The growth scan in pregnancy, checks for the baby’s position as this decides the mode of delivery. This is monitored by studying the head position of the baby. Apart from this, the doctor,

  • Records the position of the placenta
  • Assesses the amount of amniotic fluid surrounding the baby
  • Measure the abdomen and thigh bone
  • Observes the baby’s activity
  • Measures the blood flow in the umbilical cord using doppler ultrasound
  • Studies the structural anatomy of the baby

The head circumference, abdomen circumference, and thigh bone measurements allow the doctor to estimate the fetal weight. All the measurements are plotted on a chart against the normal range to assess the fetal growth in your third-trimester scan. Because babies grow at different rates from week to week, a series of scans can be more helpful than just one.

Fetal Growth Scan in Chennai

Chennai Women’s Clinic at T. Nagar  is the top choice for Fetal Growth Scan in Chennai by many moms-to-be. Our scan centre is a highly professionalized and well-equipped pregnancy scan centre in Chennai that functions under the guidance of an award-winning Obstetrician and Gynecologist in the city, Dr Deepthi Jammi (Founder & Fetal Medical Consultant, Chennai Women’s Clinic).

Why is a Fetal Growth Scan Needed in the Third Trimester?

The mother will be offered a growth and fetal wellbeing scan between 28 weeks and 32 weeks of pregnancy. This will show the doctor how the baby is growing. The most common reason for a growth scan in pregnancy is to check that the baby grows normally.

Growth Scan Procedure - What Happens During A Fetal Growth Scan?

During the fetal growth scan, various measurements are taken of the fetus. The measurements are plotted on a growth chart according to the number of weeks pregnant that the patient is at the time of the scan (gestational age). The main fetal measurements taken for a growth scan include:

  • Biparietal diameter (BPD) measures across the head
  • Head Circumference (HC) – measures around the head
  • Abdominal Circumference (AC) – measures around the abdomen
  • Femur Length (FL) – measures the length of the thigh bone

An estimate of fetal weight (EFW) can be calculated by combining the above measurements. The EFW is plotted on a graph to help determine whether the fetus is average, larger or smaller in size for its gestational age. If the fetal weight estimate is below the bottom 10% line on the graph, it is considered to be small for gestational age (SGA). If the fetal weight is above the top 10 per cent line on the graph, it is considered to be significant for gestational age (LGA).

It is important to note that repeated ultrasound measurements of the same fetus can vary, and the estimated fetal weight may be incorrect by as much as 20 per cent.

Small for gestational age (SGA)

The baby has an average head size but a trim abdomen. Most fetuses that are shown to be small for gestational age are healthy but tend to grow in a lesser range from the beginning of pregnancy. This can be when the baby is not getting a good food supply from the placenta. Some may require further ultrasound assessment to ensure that they grow as expected. Other ultrasound tests can also be performed, such as checking the amount of amniotic fluid around the fetus and measuring the blood flow in the umbilical cord (umbilical artery Doppler).

Large for gestational age (LGA)

This is when the baby has an average head size but a prominent abdomen. They get a good food supply from the placenta. And most fetuses that are shown to be large for gestational age on growth scan are well-nourished and healthy at birth. In some cases, there is an underlying cause for the fetus to be large, such as increased amniotic fluid level, maternal diabetes, or a genetic syndrome.

What are the other Observations done in a Growth Scan?

After the  growth scan procedure, your doctor would be able to conclude on,

  • Whether the dates are proper: After 20 weeks, babies become more individual in size and shape. If the baby is smaller or bigger than average at, say, 34 weeks, it doesn’t mean the baby is younger or older. The due date needs to be established by 20 weeks.
  • Where bleeding is coming from: Bleeding in the third trimester may be coming from the cervix or further inside the womb. A scan can reassure that the baby is not affected by the bleed, but the scan can rarely see its cause. The scan can detect the cause only if it is due to a low-lying placenta.
  • How much the baby weighs: The bigger the baby and the nearer to term, the harder it becomes to assess the weight.

How accurate are fetal growth scans?

Scans are usually accurate for assessing the baby’s size in the first half of the pregnancy. By the time the mother is in the later stages of pregnancy, scans remain accurate, as long as the baby is small or of average size. The closer it gets to the due date, the bigger the baby is, the harder it will be to record measurements.

The baby’s head may be too low in the pelvis in late pregnancy to get a measurement. Even if the baby’s abdomen can be measured, it’s tough to consider other factors, such as how long the baby is.

What Is Fetal Growth Restriction (FGR)?

Fetal growth restriction (FGR) is a term used to describe a fetus not growing adequately before birth. Or if the baby has a drop in the growth pattern during the later phases of your pregnancy. It is also called intrauterine growth restriction (IUGR), and the babies are called Growth restricted babies. 

FGR may only become evident after two or more ultrasounds have been performed. Due to the variation of ultrasound measurements, a minimum of two weeks is required between fetal growth scans. Other signs that may indicate FGR are umbilical cord blood flow changes and reduced amniotic fluid volume.

How Is Fetal Growth Restriction Managed?

The doctor may recommend tests if a fetal growth scan shows some anomalies. Tests that offered include:

  • an extended ultrasound assessment to check for major structural abnormalities
  • an amniocentesis to identify if the baby has a chromosomal abnormality
  • a maternal blood test to check for infection.

The pregnancy will be monitored closely with regular ultrasounds to measure:

  • On-going fetal GrowthGrowth (usually every two weeks)
  • The umbilical artery blood flow using Doppler ultrasound
  • Other blood flow Doppler studies as indicated
  • The amniotic fluid volume.

Fetal heart rate monitoring by cardiotocograph (CTG) may be performed. If the fetal condition is considered poor and the continuation of the pregnancy is not considered safe, then delivery is considered.

What if a Mother complains of reduced fetal movement?

In this scenario, the biophysical profile of a baby is studied. This includes,

  • Stretches and flexes
  • Moves his/her arms and legs frequently.
  • Opens and closes his/her hands
  • Makes breathing movements
  • Has a good heart rate 
  • Assessing amniotic fluid levels and baby’s weight.
  • Ascertaining that the baby’s movements, such as stretches and flexes, are correct.

When does a Mother get Additional Scans in the Third Trimester?

A mother might be recommended to undergo additional scans in her third trimester is:

  • When the mother complains of reduced fetal movements
  • The baby is in the breech, oblique or transverse position. To be precise, if the baby’s head isn’t down positioned when close to the delivery time. 
  • The mother is carrying twins or more.
  • The amount of amniotic fluid is more or less than it should be
  • The baby feels smaller or larger than expected for the gestational age in the fetal growth scan.
  • Shows a low lying placenta.

Important: It is not necessary to starve your stomach or fill your bladder with water before your scan. Be sure to drink enough and eat a healthy meal before you arrive. We assure you and your family members of a beautiful ultrasound visual of your baby in the womb.


Frequently Asked Questions

1.How long does a fetal growth scan take?


A fetal growth scan takes around 15-20minutes depending on the baby’s position.

2. How many times a fetal growth scan is repeated?

A fetal growth scan is not done on a routine basis to check for abnormalities. It is repeated if it shows abnormalities when scanned for the first time during your third trimester. A routine ultrasound to check for significant fetal abnormalities is performed between 18 and 20 weeks of pregnancy.

3. What happens if the baby is small during a fetal growth scan?

Such babies may have a low birth weight. For such cases, the amniotic fluid level is checked, which might be less or normal. The doctor might recommend a Doppler scan to find out why the baby is small.

4. Does a big baby in a fetal growth scan lead to C-section?

There might be chances for a c-section if the Growth of your baby is larger than it is expected to be. But, remember, estimates of your baby’s size aren’t always 100% accurate, so you need not worry much about this. 

5. Is there a fetal growth scan between 36 and 40 weeks of gestation?

The mother will get another fetal growth scan and colour Doppler studies closer to the due date (if required), between 36 and 40 weeks to:

  • Check the position of the umbilical cord
  • Measure the amount of amniotic fluid
  • Check the placental position and maturity
  • Know the baby’s position and weight
  • Check the baby’s well being and circulation
  • Assess how a previous caesarean scar appear