The 12-Week Dating Scan: What It Checks and What to Expect

For many parents, the dating scan is the first time they see their baby, and it can be both exciting and nerve-racking. Knowing what the scan checks, and what it cannot tell you, helps you feel prepared.

Imagine lying on the couch, gel cold on your tummy, holding your partner’s hand while the sonographer turns the screen. There is a flicker: a heartbeat. Then come questions about due dates, measurements and screening tests you are not sure you understand.

When the dating scan happens

The dating scan is usually offered between about 10 and 14 weeks of pregnancy, though timing differs between countries and health systems. In some places, an earlier scan is offered if there is bleeding, pain or a previous pregnancy loss.

What the scan checks

• How many weeks pregnant you are, by measuring the baby from head to bottom (crown-rump length)
• Your estimated due date
• Whether the baby’s heart is beating
• Whether you are expecting more than one baby
• Some major physical conditions, though many cannot yet be seen at this stage
• The position of the pregnancy

Why accurate dating matters

An accurate due date helps your maternity team time screening tests correctly, monitor the baby’s growth, and decide when to offer induction if your pregnancy goes beyond your due date. Dates based on scan measurements are usually more accurate than dates based on your last period.

How to prepare

• You may be asked to come with a full bladder, which can lift the womb and give a clearer picture; check your appointment letter
• Wear clothes that let you easily uncover your tummy
• Bring your pregnancy notes and any letters
• Ask whether you can bring a partner or support person and whether photos are available

What happens during the scan

Most dating scans are done through the tummy (abdominal ultrasound). The sonographer puts gel on your lower tummy and moves a probe over the skin. It is not painful, though pressure with a full bladder can be uncomfortable.,Sometimes, if the baby is hard to see, a vaginal scan is offered. A thin probe covered with a protective sheath is gently placed into the vagina. It is safe for the baby, and you can ask for a female chaperone.

Screening for chromosomal conditions

In many countries, you are offered screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome around the time of the dating scan. The combined test uses a measurement of fluid at the back of the baby’s neck (nuchal translucency), your age and a blood test to estimate the chance of these conditions.,Screening is your choice. It gives a chance, not a diagnosis. If the chance is higher, you will be offered further tests, such as NIPT or diagnostic tests like CVS or amniocentesis.

If there is a problem

Sometimes the scan shows that a pregnancy has stopped developing, which can happen without any bleeding or pain. This is called a missed miscarriage. If this happens, the team will explain what they have seen, may suggest a repeat scan to confirm, and will talk you through your options. Support is available, and it is normal to feel shocked and upset.

Questions to ask

• What is my estimated due date?
• Did you see anything that needs follow-up?
• What screening tests am I being offered, and when?
• When is my next scan?

Bleeding or pain before your scan

Light spotting is common in early pregnancy and often settles without any problem. However, bleeding can also be a sign of a threatened miscarriage or an ectopic pregnancy.

If you have bleeding, contact your midwife, maternity unit or early pregnancy unit for advice. Seek urgent help if you have heavy bleeding, severe pain, pain on one side of your tummy, shoulder-tip pain or feel faint, as these can be signs of an ectopic pregnancy.

Twins and multiple pregnancies

The dating scan is usually when twins or triplets are discovered. The sonographer will also check whether the babies share a placenta, which affects how closely your pregnancy is monitored. Twins who share a placenta need more frequent scans, often every two weeks from 16 weeks, to check for complications.

Taking care of yourself in early pregnancy

• Take folic acid daily until 12 weeks, and vitamin D throughout pregnancy, as advised in many countries
• Avoid alcohol and smoking
• Check which foods to avoid, such as unpasteurised cheese and undercooked meat
• Ask about vaccines offered in pregnancy, such as flu, whooping cough and RSV
• Rest when you can; tiredness is very common in the first trimester

Questions to ask about screening

• Which conditions does the combined test screen for?
• When will I get my screening result, and how?
• What happens if the result shows a higher chance?
• Is NIPT available to me?

Frequently asked questions

Is ultrasound safe for my baby?

Ultrasound has been used in pregnancy for decades and is considered safe when used by trained professionals.

Can I find out the sex?

Usually not reliably at the dating scan. It may be possible at the 20-week scan, depending on local policy.

Will my due date change?

Your scan date usually replaces the date calculated from your last period.

But what if I do not want screening?

That is your choice. You can still have the dating scan without screening for chromosomal conditions.

Related: Miscarriage: signs and what to expect

Sources: NHS Fetal Anomaly Screening Programme, World Health Organization antenatal care recommendations, American College of Obstetricians and Gynecologists, Royal College of Obstetricians and Gynaecologists.