Ultrasound in Pregnancy

Welcome to Women’s Ultrasound Melbourne at the Epworth Freemasons and at Tooronga Village.
All the doctors who work at WUME are highly qualified Obstetrician and Gynaecologists who have specialized further in the area of Ultrasound diagnosis and management. We are all committed to the concept of doctor self performed scans. This means that the doctor who sees you will perform the whole ultrasound examination, write the report, and will explain and discuss results directly with you.

At any time during the scan you are welcome to ask questions, though a complete answer may not be possible until the end of the scan.

What is Ultrasound?

Ultrasound examinations use sound waves that are of a higher frequency than those we can hear. These sound waves are reflected from tissue that they pass through, and are changed into an image on a TV screen by a sophisticated computer. The examination, which may sometimes be called a “scan”, allows the doctor performing the scan to examine many tissues and organs of the body, and to see normal and abnormal anatomy. It is particularly suitable for the examination of pregnancies, and especially fetal anatomy.

 

 

How is the examination performed?

Ultrasound waves are sent out from small metallic crystals within a plastic case, the ultrasound probe. Gel is first spread on the skin to allow the ultrasound waves to pass from the probe into the body. The probed is then moved over the skin. There is no pain or other sensation from the ultrasound waves.

A full bladder is not needed.

A full bladder is not required for pregnancy scans. However, a little urine in the bladder is often useful since this will often allow better views of the lower part of the uterus (womb).

What about vaginal scanning?

Vaginal scanning may be necessary in early pregnancy when the abdominal views can be very poor. To perform a vaginal scan, a thin probe is placed gently into the vagina and moved close to the cervix, where the views of the uterus are best. This is associated with minimal discomfort. In this way excellent views of fetuses as small as 2mm can be seen. After 12 weeks vaginal scanning is rarely needed. The doctor will only suggest a vaginal scan when it is necessary for diagnostic views.

Why are scans performed in pregnancy?

There are many reasons to have a scan in pregnancy, which depend on the gestation or number of weeks of pregnancy.

1. First Trimester Scans (less than 14 weeks)
It is common in early pregnancy to have a scan when the dates are unsure, or you have experienced pain or bleeding. Listed are some important reasons why your doctor might order a scan in the first few weeks of pregnancy.

1. Confirm the fetus is alive by seeing fetal heart movements
2. Calculate when the baby is due.
3. Diagnose twins or triplets.
4. Check for ovarian cysts or uterine fibroids.
5. Diagnose an ectopic pregnancy (pregnancy in the tube)
6. Screening for Down syndrome. This scan is performed between 11 and 13 weeks only. For further information see the First Trimester Down syndrome Screening Pamphlet.

2. Mid-trimester scan (18 to 20 weeks):

Most women will have a scan between 18-20 weeks. At this time the fetus is large enough to be easily seen and so detailed assessment of many structures can be made. At this stage many of the list above will also be checked.

 

 

For most women this scan will reassure them that their baby appears normal. By showing structures and organs that appear normal it is possible to rule out a large number of abnormalities. The doctor who performed the scan will reassure you that the ultrasound anatomy of the baby is normal, before you leave the scan room.

During the scan you will be shown much of the baby’s anatomical detail. The doctor will be able to show you the baby’s head and brain, the heart, stomach and bladder, the spine, the arms and legs. The baby’s movements will be seen, and you will be given a photo of your baby to take home. If you wish, you may also purchase a DVD copy of the scan for a small fee.

The scan can only assess the anatomy or structure of the baby, but in this way many of the common congenital abnormalities may be detected. In most fetuses spina bifida, cleft lip (hare lip), severe dwarfism, and major heart defects can be excluded.
For a very small number of women the scan will identify a major fetal abnormality. However, even with the best ultrasound equipment not all abnormalities can be seen. In particular, developmental delays such as intellectual delay, cerebral palsy or autism cannot be detected. If there is any problem found, the doctor who performs your scan will discuss any findings with you during the scan. The doctor may then suggest an amniocentesis to exclude possible chromosomal causes for the problem.
The placental site will also be assessed, and the pelvis inspected for any cysts or fibroids.

3. Third Trimester Scan (after 26 weeks):

Late in the pregnancy, your obstetrician may order another scan. Commonly, this will be performed to assess placental site, especially where there has been bleeding. The position of the baby’s head may suggest a breech presentation, or the doctor may be worried the baby is not growing properly. Regardless of the reason for the scan, the doctor will reassess the baby in detail each time you attend, though in later pregnancy, it may be difficult to see some parts of the baby’s anatomy.

Late in pregnancy the images of the baby will not appear as clear as at the mid trimester scan, however much useful information about the baby’s well being can still be assessed.

Late in pregnancy the images of the baby will not appear as clear as at the mid trimester scan, however much useful information about the baby’s well being can still be assessed.
To fully assess the pregnancy the baby’s weight will be estimated, measurement made of the fluid around the baby (amniotic fluid index), and the Doppler blood flows measured in the umbilical artery. These three measurements help to assess the baby’s general health.

Other investigations in pregnancy

As ultrasound gives a continuous moving picture, it is of great assistance in guiding a needle to an area within the body. Thus, procedures such as amniocentesis and chorion villous sampling are performed while watching the needle with ultrasound. These techniques are used to diagnose chromosome problems such as Down syndrome. There are pamphlets available on these procedures in the waiting room.

Does Ultrasound cause harm?

Ultrasound has been used on pregnant women for over 40 years. Despite intensive investigations by many research groups there has been no confirmed evidence of any harm to the developing baby, or to the mother. In many countries, including Australia, it is routine to have two scans per pregnancy, though more than two scans may be needed in high risk situations.