Which Pregnancy Ultrasound Scans Are Needed at Each Stage of Pregnancy?
Updated: Aug 24
Pregnancy ultrasound scans are an important part of antenatal care. Ultrasonography allows doctors to assess the developing baby, monitor growth, examine fetal anatomy and identify certain pregnancy-related concerns.
But which ultrasound scans are needed during pregnancy? Is an early scan necessary? When is the NT scan performed? What is checked during the anomaly scan? And when might you need a growth or Doppler scan?
The answer is that there is no single ultrasound schedule that applies to every pregnancy. The timing and type of scan depend on your gestational age, medical history, pregnancy risk factors and previous findings.
Here is a stage-by-stage guide to common pregnancy ultrasound scans.
What Is Ultrasonography During Pregnancy?
Ultrasonography uses high-frequency sound waves to create images of the uterus, placenta and developing baby. Unlike X-rays, diagnostic ultrasound does not use ionising radiation.
Depending on the stage of pregnancy, an ultrasound may help assess:
Pregnancy location and viability
Gestational age
Number of fetuses
Fetal anatomy
Fetal growth
Placental location
Amniotic fluid
Fetal heart activity
Blood flow when Doppler is indicated
Ultrasound is generally considered an important tool in obstetric care when performed appropriately by trained professionals.
First Trimester: Early Pregnancy and Dating Scans
During the early weeks of pregnancy, your doctor may recommend an early pregnancy ultrasound.
Depending on the gestational age, the scan can help determine:
Whether the pregnancy is located inside the uterus
Whether fetal cardiac activity is present
Gestational age
Number of fetuses
Early fetal development
A dating scan may be particularly useful when menstrual dates are uncertain or when accurate gestational-age assessment is needed.
Not every pregnancy requires an additional early scan if appropriate dating and assessment have already been established.
11–14 Weeks: NT and First-Trimester Assessment
The NT scan, or nuchal translucency scan, is performed during a specific first-trimester window.
It measures the fluid collection at the back of the fetal neck and may form part of first-trimester screening for certain chromosomal conditions.
The scan may be combined with maternal blood testing to estimate the likelihood of certain chromosomal conditions.
It is important to understand that an NT scan is a screening assessment, not a diagnostic test. A higher-risk result does not mean that the baby definitely has a chromosomal condition.
18–22 Weeks: Detailed Anomaly Scan
The anomaly scan is one of the most important ultrasound examinations during pregnancy.
It is generally performed during the second trimester and provides a detailed assessment of fetal anatomy.
The specialist may examine:
Brain and skull
Face
Spine
Heart
Chest
Abdomen
Kidneys
Bladder
Limbs
Placenta
Amniotic fluid
The NHS describes the 20-week screening scan as an examination of the baby's physical development that also checks for certain structural conditions.
Although the anomaly scan provides valuable information, no ultrasound can detect every possible fetal abnormality.
When Is a Fetal Echocardiography Needed?
Fetal echocardiography is a specialised ultrasound examination focused on the baby's heart.
It may be recommended when there is:
A suspected cardiac abnormality
A family history of congenital heart disease
A maternal or fetal risk factor
An ultrasound finding requiring further evaluation
Unlike a routine pregnancy scan, fetal echocardiography provides a more detailed assessment of fetal cardiac structures and blood flow.
Your fetal medicine specialist will determine whether this examination is appropriate for your pregnancy.
Third Trimester: Growth Scan
During the third trimester, some women may be advised to undergo a fetal growth scan.
This ultrasound assesses whether the baby is growing appropriately.
Measurements may include:
Head circumference
Abdominal circumference
Femur length
Estimated fetal weight
Amniotic fluid
Placental assessment
Growth scans are particularly useful when there are concerns about fetal growth, maternal health or other pregnancy-related factors.
However, a growth scan is not automatically required at the same frequency for every pregnancy.
When Is a Doppler Scan Needed?
Doppler ultrasound assesses blood flow through specific blood vessels.
It may be used when your doctor needs additional information about placental function or fetal circulation.
Doppler assessment may be considered in pregnancies with certain concerns, including suspected fetal growth restriction or other conditions where assessment of blood flow can provide useful information.
It should be performed when clinically indicated and interpreted together with the other findings of the pregnancy.
Do You Need 3D or 4D Ultrasound?
3D and 4D ultrasound can provide additional visual representations of the fetus. However, these technologies are not automatically required for every pregnancy.
The medical value of an ultrasound depends primarily on the clinical purpose of the examination and the expertise of the person performing and interpreting it.
If a specialised assessment is medically required, your doctor can recommend the appropriate imaging technique.
How Often Should You Have Pregnancy Ultrasounds?
There is no universal number of scans that every pregnant woman needs.
A pregnancy may include an early scan, first-trimester screening, a detailed anomaly scan and additional growth or Doppler examinations when clinically indicated.
Additional scans may be recommended if there are concerns about:
Fetal growth
Placental function
Amniotic fluid
Multiple pregnancy
Fetal anatomy
Maternal health
Previous pregnancy complications
The goal is not to perform as many scans as possible, but to perform the right ultrasound at the right time for the individual pregnancy.
How to Choose a Centre for Ultrasonography?
If you are looking for ultrasonography during pregnancy, consider a centre with experienced obstetric or fetal medicine specialists and appropriate imaging facilities.
Look for:
Qualified ultrasound specialists
Detailed pregnancy scanning protocols
Appropriate equipment
Clear reporting
Fetal medicine expertise when required
Counselling and follow-up support
The interpretation of an ultrasound is just as important as obtaining the images.
Conclusion
Pregnancy ultrasonography provides valuable information at different stages of pregnancy, from confirming early development to assessing fetal anatomy and monitoring growth.
The important point is that not every pregnancy needs the same scans or the same number of scans. Your obstetrician or fetal medicine specialist can recommend examinations according to your gestational age, medical history and individual pregnancy findings.
Whether you need an early pregnancy scan, NT scan, anomaly scan, fetal echocardiography, growth scan or Doppler assessment, understanding the purpose of each examination can help you feel more confident about your pregnancy care.
Doctor’s Note
“Ultrasound is one of the most valuable tools we have for assessing fetal development, but every scan has a specific purpose. I recommend that parents focus on having the appropriate examination at the appropriate stage rather than simply counting the number of scans. If an ultrasound identifies a concern, a detailed assessment and proper counselling can help parents understand the finding and decide whether further monitoring or investigation is needed.”
— Dr. Divya Ravikumar, MBBS, DNB (OG), MRCOG, PDF (Fetal Medicine), Fetal Medicine Specialist
FAQs
1. Which ultrasound scans are commonly done during pregnancy?
Common scans may include an early pregnancy or dating scan, NT scan, detailed anomaly scan, growth scan and Doppler assessment when clinically indicated. Some pregnancies may also require specialised examinations such as fetal echocardiography.
2. When is the anomaly scan performed?
The detailed anomaly scan is generally performed during the second trimester, commonly around 18–22 weeks. The exact timing may vary according to your pregnancy and the recommendations of your healthcare provider.
3. Is an ultrasound scan safe during pregnancy?
Diagnostic ultrasound does not use ionising radiation and has been widely used in pregnancy. It should be performed appropriately by trained professionals for a clinical purpose.
4. Do all pregnant women need a Doppler scan?
No. Doppler ultrasound is generally recommended when there is a clinical reason to assess blood flow, such as concerns about fetal growth or placental function. Your doctor will determine whether it is necessary.
5. How many ultrasound scans are needed during pregnancy?
There is no fixed number for every pregnancy. The number depends on gestational age, medical history, pregnancy risk factors and findings from previous scans. Some pregnancies require additional monitoring, while others may need fewer examinations.
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