Ultrasound in Pregnancy Guide

Ultrasonography in pregnancy is the gentle, radiation-free way that midwives and doctors check on your baby's growth and wellbeing across the months ahead. From the first dating scan to the detailed mid-pregnancy check, each scan has a purpose. This guide walks through what to expect, week by week, so the appointments feel less like a mystery and more like milestones.

What ultrasonography in pregnancy is

Ultrasonography, or ultrasound, uses high-frequency sound waves to create live images of your baby, the placenta, and the surrounding structures. A handheld probe sends sound into the body and reads the echoes that return, and a computer turns them into a moving picture on screen. According to RadiologyInfo.org, ultrasound is safe, noninvasive, and does not use radiation, which is precisely why it is the imaging of choice throughout pregnancy.

The NHS states plainly that there are no known risks to the baby or the mother from having an ultrasound scan. That reassurance is worth holding onto through what can be an anxious time. If you want the general-purpose explainer of the technology, our overview of how ultrasound works covers the basics.

The early weeks

Not every pregnancy has a scan in the very first weeks. An early ultrasound may be offered if there is uncertainty about dates, bleeding, pain, or a history that warrants a closer look. Early scans are sometimes done through the abdomen and sometimes with a transvaginal ultrasound, which can give a clearer view when the pregnancy is still very small.

These early scans can confirm that a pregnancy is in the right place, check for a heartbeat, and see whether there is more than one baby. If you have an early scan, our week-specific guides such as the 6-week ultrasound and 8-week ultrasound explain what is typically visible at each stage.

The dating scan, around 11 to 14 weeks

The first routine scan for most people is the dating scan, often called the 12-week scan. The NHS notes it usually happens between about 11 and 14 weeks and takes around 20 minutes. Its main jobs are to estimate your due date from the baby's measurements, check whether you are carrying one baby or more, and see how the pregnancy is developing.

At this appointment you may also be offered screening for certain conditions, which can include a nuchal translucency measurement combined with a blood test. Screening is optional and estimates chance rather than giving a diagnosis. Our guide to the 12-week ultrasound goes into this appointment in detail.

The anomaly scan, around 18 to 21 weeks

The mid-pregnancy scan, sometimes called the 20-week screening scan or the anomaly scan, is a detailed look at the baby's physical development. The NHS describes it as checking a set of physical conditions, along with growth, position, and whether you are carrying more than one baby. It usually takes a little longer than the dating scan.

This is often the appointment where, if you wish, you may be able to find out the baby's sex, though this depends on the clinic's policy and on the baby's position. The main purpose, though, is medical: to check that the baby is developing as expected and to plan any care that might be needed. Our detailed anatomy scan guide walks through what is examined.

Later scans and extra checks

Many pregnancies need no further routine scans after the mid-pregnancy check, but additional ultrasounds are offered when there is a reason. These might look at the baby's growth, the position of the placenta, or blood flow, particularly if there are risk factors or something to monitor.

• Growth scans: to check the baby is growing well when there is a clinical reason to watch closely.
• Placental checks: a follow-up scan may be arranged if the placenta was low-lying earlier.
• Doppler studies: to assess blood flow in the cord or placenta when needed.

If you are choosing where to have a scan, our directory on finding an ultrasound clinic explains what to ask about accreditation and reports.

How to prepare and what the scan feels like

Preparation is straightforward. Wear comfortable, two-piece clothing so your abdomen is easy to reach, and follow any instructions about drinking water. For an abdominal scan you lie on your back, the sonographer applies gel to your tummy, and moves a probe over the skin. The NHS notes an abdominal pregnancy scan typically takes around 20 to 30 minutes, and slight pressure may be applied for a clearer view.

The scan is painless and uses no radiation. Many parents find it an emotional moment, the first time they see their baby move. It is fine to bring a support person, and fine to ask the sonographer questions, though remember they need periods of quiet concentration to take careful measurements.

Abdominal and transvaginal approaches

Most pregnancy scans are done through the abdomen, but the approach can change depending on how many weeks along you are and how clear the view is.

• Transabdominal: the probe moves over the skin of your tummy with gel. This is the usual approach from the dating scan onwards.
• Transvaginal: a slim probe is gently placed into the vagina, giving a closer, clearer view. This is more common in very early pregnancy, when the baby is still tiny, and is done only with your consent.

Neither approach uses radiation, and both are considered safe in pregnancy. If a transvaginal scan is suggested, the sonographer will explain why and check that you are comfortable to go ahead. You can ask questions or decline at any point.

Common worries, gently addressed

It is natural to feel anxious about pregnancy scans, especially the mid-pregnancy check. A few reassurances tend to help. The scan does not hurt, though a full bladder can feel uncomfortable and the probe may press a little. The sonographer sometimes goes quiet while concentrating, which does not mean something is wrong; it means they are measuring carefully. And most scans bring reassuring news.

If something does need a closer look, it does not automatically signal a serious problem. Many findings are minor, need only monitoring, or resolve on their own. What matters is that you hear the meaning of any finding from your own care team, in the context of your whole pregnancy, rather than trying to interpret an image yourself.

Understanding results and choices

The sonographer takes the images and measurements, and findings are passed to your midwife or doctor, who explains what they mean for you and your pregnancy. Sometimes a scan raises a question that leads to further tests, and the NHS is clear that any follow-up testing has its own considerations that your care team will talk through with you.

A note on keepsake and bonding scans

Some private services offer keepsake or bonding scans, such as 3D or 4D images, mainly for the experience rather than for medical assessment. These can be lovely, but they are not a substitute for the medical scans your midwife arranges, and they should never be relied upon to reassure you about the baby's health. If you have any worry about your pregnancy, contact your maternity team rather than booking a keepsake scan. Our broader guide to scans during pregnancy puts all of these options in context.

Frequently asked questions

Is ultrasound safe during pregnancy?

Yes. Pregnancy ultrasound uses sound waves rather than ionizing radiation, and health authorities state there are no known risks to the baby or the mother from having an ultrasound scan. This is why ultrasound is the standard imaging used throughout pregnancy.

When are the main pregnancy scans done?

The dating scan is usually offered between about 11 and 14 weeks, and the anomaly or mid-pregnancy scan is usually offered between about 18 and 21 weeks. Additional scans may be arranged if there is a clinical reason, but many pregnancies need only these two routine scans.

Do I have to have every scan?

No. Scans are offered, not compulsory, and you can accept or decline any of them. Your antenatal care continues either way. If you are unsure, ask your midwife to explain the purpose of a scan and what the results might mean before you decide.

Can I find out my baby's sex at a scan?

Sometimes, usually at the mid-pregnancy anomaly scan, but it depends on the clinic's policy and on the baby's position on the day. The main purpose of the scan is to check the baby's development, so finding out the sex is never guaranteed.

Are private 3D or 4D keepsake scans a medical check?

No. Keepsake and bonding scans are mainly for the experience and are not a substitute for the medical scans your maternity team arranges. If you have any concern about your pregnancy, contact your midwife or doctor rather than relying on a keepsake scan.