Dating and Nuchal Translucency Scan (8-14 weeks)

At your first visit to the midwife you will be given a schedule of routine appointments and scans which you must attend throughout your pregnancy. There are two routine ultrasound scans. The first takes place between 8 and 14 weeks, although for the clearest results it should take place between 11 and 13 weeks. You will often hear this scan referred to as your '12 week scan'.

What is a nuchal translucency scan for?

The primary reason for this scan is to conduct a nuchal translucency test. The term nuchal translucency refers to a pocket of fluid which is present at the back of the baby's neck. A higher volume of fluid can be an indication that the baby may have Down's syndrome. This is not a definitive diagnosis however. It can only estimate the risk of the baby having the condition. There are two diagnostic tests available which will give a clear diagnosis; these are known as chorionic villus sampling (CVS) and amniocentesis - both of these carry risks of miscarriage.

The secondary objective of this scan is to ascertain the due date of the baby. This is done by measuring the baby's body.

Generally, your sonographer will be able to conduct the dating and nuchal translucency measurements at the same appointment, but if it is too early to get a clear image for the nuchal translucency then you will be asked to return at a later date.

Your scan will also confirm that the baby's heart is beating normally. For some parents to be, the scan can bring some exciting surprises as it will show how many babies are present!

How will I get the results?

You will be told during your appointment what your estimated due date is. This is based on the measurements of the baby. Occasionally this date is adjusted after your next scan, particularly if this scan has happened quite early.

You will have to wait a few weeks for the results of the nuchal translucency tests because the risk factor is calculated using both the scan and the results of a blood test which will be conducted separately. You will receive a letter after the results of your blood tests have been processed and the letter will tell you what the estimated chances are of your baby having Down's syndrome. If the results are considered to be low then no further tests will be conducted. Remember that this is only a calculated risk factor and there is still some chance that your baby may have the condition even if you have a low risk result. If you have a higher risk then you will be offered a diagnostic test - either CVS or amniocentesis.

How does an ultrasound scan work?

You will usually receive confirmation of your appointment by letter unless it has been arranged at very short notice. The letter will explain to you that you need to drink a certain amount of water prior to the scan (check your specific guidelines with your health team if you are unsure). This is because a full bladder will push your womb up in order to get a clearer picture for the scan.

The person conducting your appointment is called a sonographer. They will ask you to lie down on a bed and they will cover your tummy with a clear jelly. They use a hand-held device and move it backwards and forwards over your skin until they find the angle that they need. Sometimes the baby is in an awkward position for them to get the information that they require and you may be asked to encourage the baby to have a wriggle around. The sonographer may ask you to do this by raising your hips and giving them a little wiggle, or perhaps by giving a few little coughs, both of which tend to get the baby to change position. A picture is created using a high frequency sound (too high for you to hear) which is reflected back from your womb. You should be able to see the image on a screen in the room where your examination takes place.

The sonographer should explain to you what they are looking at, but do ask them if you are unclear. Your first scan is an exciting time so try to make sure that your partner can be there too. The emotional side of seeing your baby moving inside you can sometimes take people by surprise, but don't be embarrassed, it is quite normal to find the experience a little overwhelming.

Many hospitals offer the chance for you to have a printed image of the scan so make sure that you take some money with you as there is usually a small charge for this.

Is the nuchal translucency scan safe?

Yes, ultrasound scans cause no harm to you or your baby provided that they are carried out by fully trained medical staff. There are not thought to be any side effects to having an ultrasound scan. One study did show that repeated scans through a pregnancy increased the chances of the baby being left handed if it was a boy but this study has never been backed up by any further findings.