Scans During Pregnancy, Week by Week

Scans during pregnancy are the moments most parents look forward to, a chance to see your baby, hear that the heartbeat is there and check that growth is on track. Different scans happen at different stages and each one has a job to do. This guide maps the whole journey, week by week, in plain and reassuring language, so you know what is offered and why. Every pregnancy is unique, so treat this as a friendly guide rather than a rulebook, and follow the advice of your own midwife or doctor.

Why pregnancy uses ultrasound rather than other scans

Almost every routine pregnancy scan is an ultrasound, and there is a good reason for that. Ultrasound uses high frequency sound waves, not ionising radiation, so it is considered safe for use throughout pregnancy when performed for medical reasons. A sonographer moves a small probe over your abdomen, or sometimes uses a slim internal probe early on, and the echoes are turned into a moving picture on a screen. MedlinePlus notes that ultrasound has not been linked to any health harms when trained sonographers use it correctly, which is why it is the workhorse of antenatal care.

Other scans, such as x-rays and CT, use radiation and are generally avoided in pregnancy unless truly necessary. MRI is used in specific situations as a problem solving tool rather than a routine check, which we cover in our guide to MRI during pregnancy. For the everyday business of watching a baby grow, ultrasound does the job safely. If you want the general background to the technology, our overview of how ultrasound works explains it simply.

Early pregnancy: around 6 to 10 weeks

Not everyone has a scan this early. You might be offered one if you have pain, bleeding, uncertain dates, or a history that needs closer monitoring. Because the pregnancy is still tiny, an early scan is often done as a transvaginal ultrasound, where a slim probe sits closer to the uterus and gives a clearer view than scanning across the belly. Our guide to the transvaginal ultrasound explains what that feels like.

Around six to seven weeks a scan may show the pregnancy sac and, often, a tiny flickering heartbeat, though timing varies and it is common for it to be too early to see much. By eight to ten weeks the embryo is larger and easier to measure. Try not to read too much into a single very early scan. A follow up a week or two later usually gives a far clearer answer, and a slightly different date is a normal outcome rather than a worry.

The dating scan: around 11 to 14 weeks

The first routine scan for many people is the dating scan, usually offered between about eleven and fourteen weeks. Its main job is to estimate your due date by measuring the length of the baby, which is more accurate than dating from your last period. According to the NHS, this scan also checks how many babies you are carrying and confirms the heartbeat.

At this appointment you may also be offered screening for chromosomal conditions, part of which measures the fluid at the back of the baby's neck. That measurement is called nuchal translucency, and it feeds into a combined test alongside a blood sample. We explain the measurement itself in our guide to what nuchal means, and what happens on the day in our nuchal scan walkthrough.

The anomaly scan: around 18 to 21 weeks

The second routine scan, often called the anomaly or mid pregnancy scan, is usually offered between eighteen and twenty one weeks. This is a detailed look at your baby's development. The sonographer examines the brain, heart, spine, face, kidneys, abdomen and limbs, checks where the placenta is lying, and measures growth and the fluid around the baby. The NHS describes it as a check for a set of physical conditions, and it is a screening test rather than a guarantee.

Many parents also hope to learn the baby's sex at this scan. Whether this is offered depends on your clinic and country, and it is not always possible if the baby is lying awkwardly. The main purpose is health, not sex, so try to keep that in perspective. Our dedicated anatomy scan guide goes into what each organ check involves.

Later pregnancy: growth and wellbeing scans

After the anomaly scan, further scans are done only if there is a reason. Growth scans measure the baby and estimate weight, which helps if there are concerns about the baby being smaller or larger than expected. Other later scans check the position of the placenta, the amount of fluid, blood flow in the cord, or the baby's position as birth approaches.

It helps to know that growth estimates carry a margin of error, sometimes ten to fifteen per cent either way, so they guide decisions rather than give an exact birth weight. If your team recommends extra monitoring, that is careful care in action rather than a signal that something is wrong. A wider overview of the full schedule sits in our pregnancy sonogram guide.

Elective 3D and 4D scans

Some parents choose an extra 3D or 4D scan in the later weeks to see the baby's face and keep a keepsake image. A 3D scan builds a surface picture, and a 4D scan shows that picture moving in real time. These bonding scans can be lovely, and they are reasonable when done at a reputable clinic, but they are not a medical assessment and should never replace your routine care.

• Choose a clinic with qualified sonographers and clear safety practices.
• Understand that a keepsake scan will not screen for problems.
• Keep attending every standard NHS or medical appointment as well.
• Ask what happens if the sonographer happens to spot something unexpected.

How to prepare and what scans feel like

Pregnancy scans are painless. For an abdominal scan you lie back, the sonographer applies gel to your belly and glides the probe over it. You may be asked to arrive with a full bladder for early scans. A transvaginal scan uses a slim probe placed gently inside the vagina, which can feel a little odd but should not hurt, and you can ask to pause at any time. Most scans last around twenty to forty minutes depending on what is being checked and how the baby is lying.

• Wear a two piece outfit so your abdomen is easy to reach.
• Follow any instruction about a full or empty bladder.
• Bring your maternity notes and any previous scan reports.
• A partner or supporter is usually welcome, though clinics may limit numbers.

Understanding results and staying safe

During the scan the sonographer concentrates on measuring and checking, and may be quiet while working. Some results are shared straight away, while screening results that involve blood tests or specialist review come later. If the sonographer wants a colleague to take a second look, that is a normal part of careful practice and not automatically a sign of trouble.

Ultrasound is very good but not perfect. A normal scan is reassuring but cannot promise everything is or will remain fine, and screening tests give probabilities rather than certainties. That is exactly why your midwife and doctor look at the whole picture together: your history, your blood tests and your scans.

Frequently asked questions

How many scans will I have during pregnancy?

Many pregnancies include at least two routine scans, a dating scan around 11 to 14 weeks and an anomaly scan around 18 to 21 weeks. You may be offered more if there is a medical reason, such as bleeding, uncertain dates or a need to check growth. Your midwife or doctor will advise what is right for your pregnancy.

Are pregnancy scans safe for my baby?

Yes, when done for medical reasons by trained staff. Ultrasound uses sound waves rather than radiation, and it has been used in pregnancy for decades with no evidence of harm. Health bodies do advise that scans are performed when medically indicated rather than purely for souvenir images.

What is the difference between a dating scan and an anomaly scan?

A dating scan around 11 to 14 weeks confirms how far along you are, how many babies there are, and the heartbeat. The anomaly scan around 18 to 21 weeks is a much more detailed check of the baby's organs and development. They happen at different stages and answer different questions.

Will I need scans in the third trimester?

Not everyone does. Extra scans later in pregnancy are offered when there is a reason, such as checking the baby's growth, the position of the placenta, or the baby's position before birth. If your team suggests one, it is part of careful monitoring rather than a cause for alarm.

Do I have to have every scan I am offered?

No. Antenatal scans and screening are offered to you, and you can choose to accept all, some or none of them. It helps to talk through the purpose of each scan with your midwife so your choice fits what matters to you. There is no obligation to have screening you do not want.