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Growth Scans: A Brief Introduction
Pregnancy is often an exciting and sometimes anxious time for parents, particularly if it’s your first time. In the UK healthcare system, the NHS, most pregnant women with low-risk pregnancies will be offered 2 ultrasound scans within their pregnancy; the dating scan, also called the 12 week scan in the first trimester and the anomaly scan, sometimes called the 20-week scan in the second trimester.
Some women may be offered additional scans to track the progression of their baby. This can be due to a wide range of reasons, such as having higher risk factors for certain problems, including gestational diabetes or recurrent miscarriage.
These scans are commonly referred to as growth scans. They can provide maternity care providers or the midwife looking after the pregnancy with useful information about the baby, including the size and the estimated weight. This information and your history and background can be used to make informed decisions about your pregnancy plan, birth and beyond. The growth scans are typically performed anytime in the 2nd or 3rd trimester. The can be either a 24-week growth scan, a 28-week growth scan or a 32-week growth scan.
Most women, however, are not routinely offered a growth scan in their pregnancy as they are seen to be low-risk. However, a large number prefer to have additional scans. This could be for additional and reassurance and peace of mind, to check in on the baby’s progression or sometimes simply to spend more time connecting and bonding with their little one.
These women have these additional growth scans privately, such as in a private clinic or private hospital. This allows parents to see their little one in perhaps more plush surroundings and often on large high-end television screens. They can watch the baby’s heartbeat, see them wiggle or take a drink and perhaps yawn when the baby is sleepy! These scans can also confirm the sex of the baby.
In this article, I will discuss what growth scans are all about and cover questions like why they may be performed, how they are performed and what the results process looks like including how accurate they are.
What is a growth scan?
Let’s start here.
A growth scan is a medical imaging procedure performed during pregnancy. It is used to assess the growth and development of the baby and is performed with an ultrasound machine, which uses high-frequency sound waves to create images of the developing baby and the structures inside the womb. Ultrasound is a safe, non-invasive tool that can provide information to the sonographer about the baby’s development.
It is typically scheduled in the 2nd trimester or 3rd trimester and could be from 24 weeks, 28 weeks, 32 weeks or 36 weeks depending on the care pathway you are on.
During a growth scan, the sonographer, a healthcare professional specialising in performing ultrasound scans, will measure various parts of the baby to evaluate the baby’s size, weight, and overall growth. These measurements often include the baby’s:
- Head circumference (HC)
- Abdominal circumference (AC
- The length of the thigh bone (FL)
These measurements are used to calculate the baby’s weight. This is also referred to as the estimated fetal weight. The sonographer will compare these measurements to standardised growth charts to determine if the baby’s growth is within the expected range for their gestational age.
Growth scans in pregnancy are usually scheduled at specific points during the pregnancy, such as around 24 weeks, 28 weeks, 32 weeks, and 36 weeks, although the timing may vary depending on the specific circumstances and medical history of the mother.
By monitoring the baby’s growth with growth scans, the maternity team can identify any potential issues or abnormalities early on which allows for appropriate management and interventions, if necessary.
What happens during a growth scan in pregnancy?
A typical growth scan could look like this:
Preparation for the scan
You may be asked to have a full bladder before the scan, especially in the early 2nd trimester, as this can provide better visualization of the uterus and fetus. However, in the late 2nd and 3rd trimesters, a full bladder may not be needed. The specific preparation instructions may vary depending on the hospital or clinic and the purpose of the scan.
Ultrasound scan procedure
You will be asked to lie down on an examination couch, and a clear gel will be applied to your tummy. The gel acts as a lubricant to help the ultrasound probe make better contact with your skin and allows sound passage into the abdomen. The sonographer will then move the probe over your abdomen to obtain images of the baby and if necessary your womb. Sometimes they may need to press into your tummy to get clearer images however, this should not be painful.
Measurements and observations
The sonographer will take various measurements to assess the growth of the fetus. These measurements typically include the baby’s head circumference, abdominal circumference, and thigh bone (femur) length. They may also examine some of the baby’s organs, blood flow, and amniotic fluid levels. The sex of the baby or gender can also often be seen if this is required.
As the scan progresses, the sonographer may point out different structures and features of the baby. They may explain what they are looking at and discuss any findings.
The measurements and observations will be recorded in a report or the mother’s medical records. These records help track the baby’s growth over time and serve as a reference for future scans.
Discussion of results
After the scan, the sonographer may discuss the initial findings with you or make the results available for your midwife to review in more detail. They will be able to provide information about the baby’s growth, estimated weight, and any potential concerns that require further evaluation or monitoring.
The duration of these types of baby private pregnancy scans can vary but typically lasts around 15 to 20 minutes, depending on the examination’s complexity and the baby’s position. In some cases, where the baby is not in a good position or if the maternal BMI is high, it may be more difficult to get clear images and the scan could take longer.
What can you find in a growth scan NHS or private?
During a growth scan, various aspects of the baby can be assessed. Here are some common things that can be observed:
Fetal size and growth
The primary purpose of a growth scan is to evaluate the size and growth of the fetus. The measurements taken during the scan, such as the head circumference, abdominal circumference, and femur length, can help determine if the baby’s growth is within the expected range for its gestational age.
Estimated fetal weight
Healthcare providers can use specialised software or calculators to estimate the baby’s weight based on the measurements taken during the scan. This can help assess whether the baby is growing appropriately or if there are concerns about growth restriction or excessive growth.
The growth scan can also determine the location and position of the placenta, which is important for assessing potential complications such as when the placenta covers the cervix (placenta previa). It may also be able to check if the placenta is working well or where the placenta is not working efficiently (placental insufficiency).
Amniotic fluid levels
The amount of amniotic fluid surrounding the baby is evaluated during a growth scan. Too little or too much amniotic fluid can indicate potential issues that may affect the baby’s well-being.
Fetal position (presentation)
The growth scan can help determine the baby’s position in the womb, including whether the baby is in a head-down (cephalic) position or a head-up (breech) position where the buttocks or feet are closest to the cervix. This information is important for planning the method of delivery.
While the primary focus of a growth scan is on assessing growth, it may also reveal some structural abnormalities or markers that require further tests. It is however important to mention that a growth scan is not a comprehensive detailed fetal anomaly scan, which is a separate ultrasound examination specifically dedicated to identifying structural abnormalities.
How accurate are growth scans?
Generally, pregnancy growth scans are considered an accurate and reliable tool for assessing fetal growth and development. However, like any medical test, some limitations and factors can affect their accuracy. Below I have listed a few points of consideration regarding the accuracy of growth scans:
- Gestational age estimation: The accuracy of growth scans depends on the accurate estimation of gestational age. Uncertainty regarding the date of conception or irregular menstrual cycles may affect the accuracy of the growth scan assessment.
- Fetal position and cooperation: The position of the fetus during the scan can impact the ability to obtain accurate measurements. Sometimes, the baby’s position, movements, or presence of hands or feet in front of certain structures can make it challenging to obtain accurate measurements.
- Maternal factors: Certain maternal factors, such as maternal obesity, can affect the quality of the scan and make it harder to see the baby and obtain accurate measurements. Conditions like diabetes or high blood pressure can also affect fetal growth and these factors may need to be taken into account when interpreting the growth scan results.
- Variability in fetal growth: Fetal growth is a changing and dynamic process. There can be natural variations in growth patterns among different babies. Growth scans provide estimates based on population-based growth charts, but individual variations can and do occur.
- Equipment and imaging quality: The accuracy of growth scans can also be influenced by the quality and capabilities of the ultrasound equipment used. Higher-resolution machines can provide clearer images and better measurements, leading to improved accuracy.
- Sonographer expertise: The accuracy of the growth scan can be influenced by the sonographer’s or healthcare provider’s experience and expertise performing the scan. A skilled operator who is familiar with the technique and has expertise in fetal ultrasound can enhance the accuracy of the measurements.
Growth scans in pregnancy are generally reliable however they are not infallible, and there can be instances where growth abnormalities are missed or incorrectly identified. It is essential to remember that growth scans are part of a comprehensive approach to monitoring fetal well-being, and they are typically interpreted in conjunction with other clinical information and tests.
What do the results look like?
The results will typically include all the measurements taken during the scan, including the head circumference, abdominal circumference, and femur length, and the estimated fetal weight. It will also include information about the baby’s position, amniotic fluid, the placenta, and the baby’s movements. There may be other information about the pregnancy such as Doppler (blood flow to baby) or other characteristics seen during the scan with comments about the size of the baby. Graphs showing the baby’s measurements and weight are commonly included and are a good visual tool for assessing the growth rate.
The report is typically printed for you following your appointment and placed in your maternity file. The sonographer will share their findings with you verbally and answer any questions you may have about the results.
Sometimes additional scans and/or additional tests may be needed to review the progress of the pregnancy, particularly if your baby is smaller or larger than expected. If this is the case, try not to panic! This does not necessarily mean there is a problem and often there are no underlying concerns as every baby grows at their own pace and there can often be significant variations.
Growth scan at 32 weeks
For some women, a growth scan may be scheduled at 32 weeks. Commonly a 32 week growth scan is performed if:
- there are concerns about the baby’s growth
- the midwife thinks the mother’s bump is not large enough (fundal height)
- the mother has certain medical conditions (such as diabetes or high blood pressure)
- if there are other risk factors that may affect fetal development.
- if the mother is not feeling fetal movements.
Of course, this can be an anxious time for the mother, however, most of the time the scan offers additional reassurance that all is going well and the baby is developing as expected.
How to book a private growth scan?
Private scans can often complement your NHS scans and the results can be shared with your maternity care providers. Growth scans are safe and a good method for checking in on the pregnancy to ensure it progresses well in the second and third trimesters.
Arranging a growth scan in pregnancy privately is easy these days as many private clinics are performing these types of scans, often at a very reasonable price. Typically many private clinics have large televisions connected to the ultrasound machine to make it easier for parents to see their baby and many will talk them through the scan. They are usually comfortable and clean, designed to make the experience less stressful. However, it is important to use a reputable and trusted clinic that has specialist staff that can perform these scans effectively. Our staff either currently work for or have worked in the NHS. They have had plenty of experience having performed thousands of growth scans in their career.