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.

Morphology scans check your baby for any physical abnormalities.

What is an morphology scan and what does it look for?

The morphology scan is a detailed ultrasound scan that looks at your baby’s body and observes the position of the placenta, the umbilical cord, the amniotic fluid around your baby, and your uterus and your cervix. It is also known as a ‘anomaly scan’ or a ‘18-20 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, stomach, kidneys and limbs. It is important to know that while many abnormalities are picked up by this scan, not all of them are.

The sonographer can often tell if you are having a boy or a girl, with about 95% accuracy. 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 18-20 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.

When is an morphology scan performed?

An morphology scan is performed in the second trimester, usually at around 18-22 weeks of pregnancy.

How is an morphology scan performed?

The sonographer will place some gel on your belly and move a transducer across it in order 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.

Many parents find that they feel more attached to their baby after seeing them at this scan. It’s a good idea to share the experience with your partner or support person. A medical certificate can usually be provided so that you can take time off work for the scan.

What can an morphology scan show?

You might be able to see your baby’s heart beating, a clear image of your baby’s spine, and your baby’s arms and legs waving and kicking. Some babies may even be sucking their thumb. The images look a bit like a blurry photo.

Do I have to have the scan?

No, you do not have to have the scan. It’s your choice. If you are not sure, you can call Pregnancy, Birth and Baby on 1800 882 436 (free call from landlines) if you would like to discuss your options further.

What do the results mean and what happens next?

The sonographer might not give you much information about your pregnancy and baby while you are viewing the scan. A detailed scan report will be sent to your doctor or midwife, so you will need to see them to discuss the results.

If abnormalities are suspected or detected, you may need to have further tests. Your doctor or midwife will explain the options to you and may recommend that you speak with a genetic counsellor, an obstetrician or a paediatrician.

Sources: , Australian Government Department of Health(Guidelines for the use of ultrasound in the management of obstetric conditions: 18-22 week detailed morphology scan) Murdoch Children's Research Institute (A Decision Aid: Testing in pregnancy for fetal abnormalities) , Raising Children Network (Tests in pregnancy) , Raising Children Network (When your unborn baby has chromosomal abnormalities or disability)