Ultrasound in Pregnancy: Why It’s Important and When It’s Done

Medical Writer: Janefrances Ugochi Ozoilo, MBBS, FMCPH, MSc (PH), PMP

Medical Reviewer: Azuka Chinweokwu Ezeike, MBBS, FWACS, FMCOG, MSc (PH)

Highlights

• An ultrasound during pregnancy is a safe and easy way to see your baby and check how the pregnancy is going.
• It helps check important things early, like the baby's heartbeat, due date, pregnancy progress, and whether there is more than one baby.
• Ultrasounds during pregnancy also check the baby's growth and development, the placenta, amniotic fluid, and some birth or chromosomal issues.
• An early scan is usually done between 11 and 14 weeks. A mid-pregnancy scan happens between 18 and 21 weeks. Later scans are done if needed for medical reasons.
• During the scan, a probe and gel work together to create detailed images of the baby. 
• While you may experience mild discomfort from the probe's pressure, the procedure itself is safe and painless.

What is a Pregnancy Ultrasound?

An ultrasound during pregnancy is a safe test that uses sound waves to create images of the baby, placenta, and womb (uterus). Getting a pregnancy ultrasound is a simple and safe way to see how your baby is doing. It is an important part of your pregnancy care. It checks how your pregnancy is progressing, gives useful information about your baby's growth, and can find problems early.

For many pregnant women and their families, it is also one of the most exciting times of pregnancy because it makes everything feel more real. Knowing what an ultrasound is, why it is done, and when to expect it can make your pregnancy experience less confusing and more comforting.

10 Reasons for an Ultrasound in Pregnancy

• Early ultrasound checks if a pregnancy is developing inside your womb. 
• It looks at your baby's growth, heartbeat, and checks for issues like pain, bleeding, miscarriage, or pregnancy outside the uterus.
• Early ultrasound helps determine how far along your pregnancy is and your due date, especially if your last period date is unclear.
• To see if you are having more than one baby
• In pregnancies with more than one baby, an ultrasound checks if the babies share a placenta or have separate ones. This helps doctors decide how to monitor the pregnancy.
• In the first trimester, an ultrasound can be used with other tests to screen for conditions such as Down syndrome, Edwards syndrome, and Patau syndrome.
• The mid-pregnancy scan checks for abnormalities in the internal organs of your baby. It is also called an anomaly scan.
• Ultrasound can check the placenta and amniotic fluid of your pregnancy. It shows where the placenta is and if it is low. It also checks whether the amount of amniotic fluid is normal.
• Some ultrasound methods, such as Doppler ultrasound, can assess blood flow to the placenta.
• Ultrasound helps guide procedures like amniocentesis and chorionic villus sampling [1].

When Ultrasounds Are Done in Pregnancy

The World Health Organisation (WHO) advises having one ultrasound before 24 weeks of pregnancy. This helps confirm pregnancy progress, detect multiple babies, identify any baby problems, avoid late pregnancy inductions, and improve the pregnancy experience [2].

Early Pregnancy Ultrasound 

This is usually the first ultrasound in pregnancy. It is often done between 11 and 14 weeks [3]. It is done to:

• Make sure the baby is alive and growing.
• Find out how many weeks pregnant you are.
• Calculate your due date more accurately.
• See if you are having more than one baby.
• Check early development and the pregnancy's location.

Mid Pregnancy Ultrasound

The mid-pregnancy scan, done between 18 and 21 weeks, checks how the baby is growing [3]. It looks at the brain, spine, face, heart, belly, bones, and kidneys. This is also known as the anatomy/anomaly scan.This scan checks for:

• Anencephaly: This is when a baby’s brain and skull do not fully form. 
• Spina bifida: This is when the baby’s spine does not close all the way. 
• Cleft lip: This is when there is a gap in the baby’s upper lip. 
• Congenital diaphragmatic hernia: This is a hole in the muscle under the lungs, allowing some organs to move into the chest. 
• Gastroschisis: This is when the baby’s intestines grow outside the belly through a small opening. 
• Exomphalos: This is when some organs grow outside the belly but are covered by a thin sac. 
• Serious cardiac conditions: These are major problems with the baby’s heart formation or function. 
• Bilateral renal agenesis: This is when both kidneys do not form. 
• Severe skeletal dysplasia: This means the baby’s bones do not grow normally. 
• Edwards’ syndrome: This is a genetic condition caused by an extra copy of chromosome 18. 
• Patau’s syndrome: This is a genetic condition caused by an extra chromosome 13.

It's important to remember that the ultrasound scan might not detect every condition.

Late Pregnancy Ultrasound

A later scan is usually done if there is a specific concern or medical reason [4]. It may be used to:

• Check how the baby is growing
• Observe your baby's position and presentation, especially near delivery. Some babies change position and presentation towards the end of the pregnancy.
• Check where the placenta is
• Monitor twins or pregnancies that need more attention

What Happens During an Ultrasound Scan

Routine ultrasounds do not harm the baby and help check the baby's growth. Internal scans, like a transvaginal ultrasound, are also safe but may feel a bit uncomfortable. Most scans take between 10 and 45 minutes, depending on the needs.

• For abdominal scans, you will need to have a full bladder. For some early transvaginal scans, you might need to empty your bladder first. Your doctor will tell you what to do before the appointment.
• When you go for an ultrasound, you will usually lie down on a bed next to the machine. The sonographer or healthcare professional will make sure you're comfortable before starting the scan.
• A small amount of gel will be put on your belly. The gel might feel cold, but it helps the probe move easily and makes the pictures clearer. The gel is water-based and safe.
• A device called a probe will be moved over your belly. It sends sound waves to show pictures of the baby on a screen.
• The room lights might be turned down to make the pictures easier to see. 
• The sonographer might stop during the scan to take measurements or write notes.
• You may need to change position during the scan. This helps the sonographer obtain clearer images of the baby or placenta.
• Gentle pressure is needed. It might feel uncomfortable if your bladder is full, but it should not be painful.
• In early pregnancy, you might have a transvaginal ultrasound. A thin probe goes into the vagina to get a clearer image. It might feel uncomfortable, but not painful [3].

If you feel pain, feel too uncomfortable, or want the scan to stop, you can tell the person doing the scan at any time.

Are Pregnancy Ultrasounds Safe?

Pregnancy ultrasound scans are generally safe. They use sound waves to make pictures of your baby, not radiation like X-rays or CT scans. Major medical groups say there is no proof that routine ultrasound harms a developing baby when used correctly during pregnancy care [5].

During the scan, you might feel some pressure on your stomach and a bit of discomfort, but it's usually not painful. Most of the time, the procedure is quick, and the scan helps your doctor check your baby's growth, position, and progress.

Conclusion

Pregnancy ultrasounds are important and safe. It lets you see your baby and helps doctors check your baby's growth. It can also find problems early. Knowing about ultrasounds can help you feel informed and involved during your pregnancy.

Frequently Asked Questions (FAQs)

1. Can I bring my partner or a family member to the scan?
In many hospitals, you may be allowed to bring your partner or a family member, but this depends on the hospital or scan centre’s policy.

2. Will I get a picture of my baby after the scan?
Some scan centres give printed images or digital copies, while others may charge a small fee or have different rules.

3. Can an ultrasound tell the sex of the baby?
Sometimes it can, especially later in pregnancy, but it depends on the baby’s position and the facility's policy.

4. What should I wear to my ultrasound appointment?
It is usually best to wear comfortable two-piece clothing so your tummy can be easily reached during the scan.

5. What happens if the sonographer cannot see everything clearly?
You may be asked to change position, walk around a little, or come back for another scan to get clearer pictures.

References

1. Murugan VA, Murphy BO, Dupuis C, et al. Role of ultrasound in the evaluation of first-trimester pregnancies in the acute setting. Ultrasonography 2020; 39: 178–189. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC7065984/

2. Imaging ultrasound before 24 weeks of pregnancy: 2022 update to the WHO antenatal care recommendations for a positive pregnancy experience. Available from: https://www.who.int/publications/i/item/9789240051461.

3. Ultrasound scans in pregnancy. NHS.UK, Available from: https://www.nhs.uk/pregnncy/your-pregnancy-care/ultrasound-scans/ 2020.

4. What complications can affect the placenta? NHS.UK, Available from: https://www.nhs.uk/pregnancy/labour-and-birth/placenta-complications/ 2020.

5. Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation: Correction. Obstetrics & Gynaecology 2018; 132: 786–786.Available from: https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/10/guidelines-for-diagnostic-imaging-during-pregnancy-and-lactatio

Disclaimer:
The information provided on this website is for general educational and informational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Published March 24, 2026