Why is anomaly scan done

Error: Not a valid value. In the second trimester of pregnancy, your doctor or midwife might offer you an ultrasound scan called an morphology scan. The scan is performed by a specialist sonographer, a health professional trained in the use of ultrasound. This page explains what you can expect, and what the scan might show. It is also known as a 'anomaly scan' or an '18 to 20 week scan'.

The sonographer will measure the baby and use these measurements to confirm the expected date of birth. The sonographer will also check to see if your baby has any abnormalities in their growth or development, including in their heart, spine, stomach, kidneys and limbs. It is important to know that while many abnormalities are picked up by this scan, not all of them are. If you prefer to wait until the birth to find out the sex of your baby, it's a good idea to ask the sonographer not to mention it.

If your placenta is positioned low in your uterus, your doctor or midwife will tell you that you have a low lying placenta, also known as placenta praevia. Usually another ultrasound is recommended in the third trimester , to check that your placenta has moved away from your cervix.

A low lying placenta at 18 to 20 weeks does not necessarily mean that it will be low at the time of birth, so there is no cause for concern. If your placenta is close to your cervix in the third trimester, there may be an increased risk of bleeding during labour.

If this is the case, your doctor or midwife will discuss with you what your options are for the birth. An morphology scan is performed in the second trimester , usually at around 18 to 20 weeks of pregnancy. The sonographer will place some gel on your belly and move a small handheld device called a transducer across it to obtain images of your baby on a screen.

The scan takes about half an hour. You might be offered a photo or a DVD of the scan. The amniotic fluid surrounding your baby will look black.

Most serious abnormalities can be detected on a scan. However, it is not possible to see all problems and some will only be found after birth. Some conditions such as cerebral palsy and autism will never be seen on a scan. The quality of the scan image depends on many factors, including the position of the baby and the size of the mother. For example, it will be more difficult to see the baby clearly if the mother is overweight.

A poor image will affect our ability to see problems. The doctor will look at the placenta after birth. The placenta will be described as low if it reaches down to or covers the neck of your uterus your cervix. Below is a list of different types of congenital abnormality, and how likely scanning is to identify each problem.

This means that even if your scan is normal there is a small chance that your baby will still have a problem. Some conditions, including certain heart defects and bowel obstructions, may not be seen until later in your pregnancy. Having your anomaly scan will most likely rule out all these conditions, as the vast majority of babies are born healthy. Sometimes babies with chromosomal abnormalities have signs called ultrasound markers.

While some babies with chromosomal abnormalities have these markers, it is important to remember that many normal babies also have these signs. The only way to diagnose or exclude a chromosomal problem for certain is to have an amniocentesis. In this article What is an anomaly scan? Do I have to have an anomaly scan? What will I be able to see on the scan? Can I have a photo of my scan?

Can I record my scan on my phone? What will the sonographer look at on my scan? Which conditions can be seen on the scan? Why have I been asked to have another anomaly scan? What if there are signs of a problem on my scan?

Thinking of having a 3D ultrasound scan during your pregnancy? Find out if it's safe for your baby in this video. More pregnancy videos.

References ACOG. Methods for estimating the due date. Congenital heart disease: prenatal screening, diagnosis, and management. Prenatal assessment of gestational age, date of delivery, and fetal weight. Should we find out the sex of our baby? NCT, Pregnancy. If antenatal screening tests find something. NHS, Pregnancy. The week screening scan can sometimes find the baby has a health condition. You may like someone to come with you to the scan appointment.

Most hospitals do not allow children to attend scans as childcare is not usually available. Ask your hospital about this before your appointment. There are no known risks to the baby or you from having an ultrasound scan, but it's important to think carefully about whether to have the scan or not. It may provide information that may mean you have to make some important decisions. For example, you may be offered further tests that have a risk of miscarriage, and you'll need to decide whether or not to have these tests.

No — it's your choice whether to have it or not. Some people want to find out if their baby has a condition, and some do not. If any condition is found or suspected, the sonographer may ask for another member of staff to look at the scan and give a second opinion. Scans cannot find all conditions, and there's always a chance that a baby may be born with a health issue that scans could not have seen.

If the scan shows there might be something, you may be offered another test to find out for certain. If you're offered further tests, you'll be given more information about the tests so you can decide whether or not you want to have them. You'll be able to discuss this with your midwife or consultant.

If necessary, you'll be referred to a specialist, possibly in another hospital. Page last reviewed: 7 April Next review due: 7 April