What is a Fetal Growth Scan?
The growth scan, or positioning scan, is an ultrasound that is done to assess the baby’s growth and development. It is typically carried out between 23 and 40 weeks of pregnancy.
This scan measures the baby’s head circumference, abdomen circumference, and thigh bone measurements allowing 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.
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
Growth Scan at Jammi Scans
Why is a Fetal Growth Scan Needed in the Third Trimester?
Fetal growth scan is prescribed around 28 and 32 weeks of pregnancy to ensure the baby’s health and growth.
This scan is mainly done to make sure that the baby is growing normally.
Growth Scan Procedure - What Happens During A Fetal Growth Scan?
A fetal growth scan is usually done along with a fetal doppler scan. A growth scan assesses the factors including the fetus’s growth, development, and size, while a Doppler scan evaluates the factors including blood flow and oxygen supply to the fetus.
During a fetal growth scan, the doctor measures the fetus’s head, abdomen and thigh measurements. 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 can have a around 20% of difference.
Is the growth scan and doppler scan the same?
Although a growth scan and a Doppler scan are not the same, they are often performed together. A growth scan assesses the factors including the fetus’s growth, development, and size, while a Doppler scan evaluates the factors including blood flow and oxygen supply to the fetus.
Small For Gestational Age (SGA)
SGA or Small For Gestational Age term is used when the fetus is smaller than other fetuses of the same gestational age. These babies can be smaller than 90% of other babies within the same gestational age.
SGA can be due to various factors including:
- Placental issues
- Malnutrition
- Maternal health issues
If the baby is too small, the healthcare expert might prescribe further screening to assess the baby’s growth and development.
Large For Gestational Age (LGA)
LGA or Large For Gestational Age term is used when the fetus is larger than other fetuses of the same gestational age. These babies can be larger than 90% of other babies within the same gestational age.
LGA can be caused due to various factors including:
- Maternal health issues including gestational diabetes
- Genetic issues
- Mother being obese or overweight
What Are The Other Observations Done In A Growth Scan?
Apart from the fetus’s growth and development, there are a few other metrics that are observed during a growth scan including:
- Amniotic fluid
- Placenta
- Umbilical cord
- Mother’s cervix
- Baby’s position
How Accurate Are Fetal Growth Scans?
Fetal growth scans are quite accurate with an error margin of up to 15%.
Growth scans are more accurate in the earlier stages of pregnancy than later because, as the baby grows, it gets difficult to measure the baby as the baby might move and not cooperate well.
What Is Fetal Growth Restriction (FGR)?
FGR or Fetal growth restriction means that the fetus is not growing adequately for its gestational age.
It is also called IUGR or Intrauterine growth restriction where the fetus doesn't grow to its full potential. These babies are called growth restricted babies.
If the doctor suspects FGR, they might call for further rounds of intervention to confirm it.
What If A Mother Complains Of Reduced Fetal Movement?
When a mother complains about reduced fetal movement, the doctor calls for an ultrasound to assess the baby.
They check if the baby can stretch, flex and move their arms and legs frequently. They also assess other metrics including the baby’s heart rate and amniotic levels.
When Does A Mother Get Additional Scans In The Third Trimester?
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.
When Does A Mother Get Additional Scans In The Third Trimester?
If the pregnancy is considered high-risk, the doctor calls for additional scans to ensure the baby’s health. A pregnancy is considered high-risk for various issues including:
- The age of the mother is over 35
- The mother has gestational diabetes, hypertension, obesity, pre-eclampsia
- The mother is pregnant with multiple babies such as twins and triplets
How Is Fetal Growth Restriction Managed?
Fetal Growth Management is based on how serious the fetal restriction is. Fetuses diagnosed with FGR require frequent monitoring and assessment.
It also requires medications and other interventions if and when needed.
What Causes Fetal Growth Restriction?
FGR can be caused due to various factors including:
Mother having
- Diabetes
- High blood pressure
- Anemia
- Auto-immune conditions
- Obesity
- Smoking/alcohol
- Malnutrition
- Multiple babies such as twins, triplets
Fetus has
- Infection
- Birth defects
- Chromosomal issues
Frequently Asked Questions
01. How Long Does A Fetal Growth Scan Take?
A fetal growth scan takes around 15-20 minutes depending on the baby’s position.
02. 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.
03. 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
04. 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.
05. 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
