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What is an ultrasound?

Woman having an ultrasound during early pregnancyAn ultrasound is an image familiar to most, yet many an expectant mother may have little idea of what one is and how it is conducted.

The main benefit of an ultrasound during pregnancy is that it provides a lot of information easily, at a relatively low cost and is non-invasive.

Although the clarity of the images is often not cutting edge and sometimes quite grey and unclear, it is also quick and gives a real time interpretation of the baby’s current experience.

Ultrasound remains one of our best options in terms of assessing maternal and foetal wellbeing during pregnancy.

Ultrasound images provide “slices” or images of the baby on the monitor or screen, rather than the whole baby at once – much like a slice of bread. And this is why at any one time when having an ultrasound, the baby’s head and face, and perhaps their arms are visible rather than their whole body. Different portions of the baby’s body become visible as the transducer is moved around the mother’s abdomen.

The transducer is a small device containing a small vibrating crystal which emits high frequency sound waves. These sound waves bounce off internal structures and different images are then reflected on the monitor screen, depending on the type of tissue the sound waves reflect from.

In effect, the image is created by the sounds, or echoes, which are reflected. Whilst not as clear as a photograph, they are often so lifelike that the 2D black and white images can’t be clearly interpreted.

The sound waves used are so high that they can’t be heard by the human ear and this is why the term “ultra” is used in the naming of the procedure. Other names for an ultrasound include scan, ultrasonography, or sonogram.

Where is an ultrasound performed?

Most types of ultrasound are medical procedures which are done in a radiography clinic or within the X-Ray department of a hospital. It is a process which involves high frequency sound waves feeding back information which is then interpreted by a computer and a sonographer – a health professional who is trained in ultrasound practice.

What will happen during the ultrasound?

The ultrasound process begins with special gel being squirted onto your lower abdomen, in the region between your navel and your pubic bone. Most sonographers warm the gel in a bowl of water first, so there’s not so much of a shock when it meets with the skin. This gel helps to reduce the friction and increase the contact between the transducer, or  ultrasound probe, and your skin, so that the images are clearer. This gel is a pale blue, translucent colour and is water soluble, so don’t worry if a small amount gets onto your clothing – it will wash out easily.

The transducer will be moved across your tummy until a clear image becomes available, then the sonographer will hold it there temporarily. Generally, the sonographer will hold the transducer with one hand and type information into the computer with the other. At times throughout the procedure they will pause, click on various keyboard options, fill you in on what they are doing and make some adjustments to the image. They will also take some ‘photos’ and measurements.

The appointment generally lasts around thirty minutes, give or take. The position the baby is lying in can determine how long the ultrasound takes. A considerate baby will lie reasonably still in an optimum position, however a busy, restless baby may need more careful measuring, then it becomes necessary to wait until things quieten down a little. Other factors which influence the quality of an ultrasound include the mother’s weight, her stage of pregnancy, the skill of the sonographer, and the quality of the equipment being used.

Why would I have an ultrasound?

An ultrasound can be used to check that the baby is developing as it needs to and to help diagnose any problems, to ensure the position of the baby and the placenta, and to check how many babies are present. A multiple pregnancy may be possible if a mother is large for her pregnancy dates and she or her maternity care provider become suspicious – and an ultrasound is one way to check.

Ultrasounds are commonly used during pregnancy to assess the growth and development of the baby, but they are also used for other routine medical assessments as well. Areas such as the abdomen, pelvis, muscles, joints, and even the heart and blood vessels can all be visualised through ultrasound.

If there is a problem with a baby detected via ultrasound it is very useful to know about this as soon as possible. Planning, counselling, and preparation for the birth and early post natal care can begin once ultrasound findings have been clarified. It also allows for parents to do some of their own research and feel that they have an element of control over their situation.

Are there any risks to my baby or me?

Unlike x-Rays, ultrasounds do not involve ionising radiation, so there is no risk of radiation complications. The procedure is considered to be completely safe – though it is prudent to avoid unnecessary ultrasounds in general.

Occasionally, the procedure may cause some discomfort because a mother may need to have a full bladder. But this is only for a short period of time and if it becomes too uncomfortable, the sonographer will be able to redirect the transducer so there’s not as much pressure.

Do I need to prepare anything beforehand?

You will need to locate a radiography clinic which specifically provides ultrasound services. Not all do, so make a point of checking first if you’re planning a trip to book an appointment.

As you will need to expose your belly, preferably wear pants or a skirt so you do not need to uncover too much flesh.

In the early weeks of pregnancy, the uterus lies deep in the pelvis and is covered by the bowel, so if you are having a first trimester ultrasound, you may be advised to drink 750mL to 1L of water in the hour or so preceding your ultrasound. The gas within the bowel does not allow the ultrasound waves to pass through, and so urine in the bladder helps to push the bowel away and also to ‘lift’ the uterus up out of the bony pelvis.

What is a 2D ultrasound?

A 2D ultrasound is the standard procedure used during obstetric ultrasound. It is the one used to produce 2 dimensional images of what is happening inside the mother’s and baby’s bodies. Generally, all pregnancy ultrasounds are still done using 2D technology.

The images from a 2D ultrasound tend to be in black and white and have the same level of detail as a photographic negative. 2D ultrasounds are generally performed early in gestation to diagnose a pregnancy, determine a multiple pregnancy, check where the placenta is lying, determine any physical abnormalities, and estimate birth dates. At 18-20 weeks, parents can use 2D ultrasound to determine the sex of the baby and take home clear photos.

What is a 3D ultrasound?

A 3D ultrasound takes thousands of pictures or photos of the baby at once. These are then translated by computer into 3 dimensional images which are almost as clear as a real life photograph. These ‘still’ pictures of your baby mean that you can see your baby in three dimensions, rather than two.

There is a depth and shape to a 3D image, giving clarity which is not as evident in a 2D ultrasound. This is because a 2D ultrasound sees through the baby to its internal organs and tissues, whereas with a 3D and 4D ultrasound the baby’s skin can be seen so there is more of a realistic shape and form to the images – particularly the baby’s face and delicate features.

With 3D ultrasounds, both the transducer used to transmit the sound waves and the computer software are more advanced and complex. This is why a 3D ultrasound is more expensive and generally not included in standard obstetric practice. Although it’s lovely to see the baby with a clear image, there are no real health benefits to having a 3D ultrasound when compared to a 2D one. Free public hospital and Medicare rebated scans are generally limited to 2D ultrasounds because of the additional cost of the 3D technology.

Generally, the recommended time to have a 3D ultrasound is between 26-30 weeks gestation. By this time, there is sufficient fat under the skin to see the baby’s facial appearance, rather than the supportive bony structure.

What is a 4D ultrasound?

4D or 4 dimensional scans build on the technology of 3D scans. The extra dimension is time, so that 4D ultrasounds are effectively moving images of your baby in real time. As your baby kicks, moves, frowns, grimaces, sucks their thumb, opens their eyes, or moves their lips, you will be able to see these movements on the scan as they are actually happening.

If you go to a sonography clinic which is medically run, then you will be able to make a Medicare claim on at least a portion of the fee. But if you go to a clinic which does not provide medical screening, for example those which do not claim to be ‘diagnostic’ and are instead ‘entertainment’, then you will need to pay all costs yourself, ranging from $100-$200. Clinics vary in their recommendation of the best time to have a 4D ultrasound, some state between 27-32 weeks of gestation and others state between 26- 30 weeks.

Image credit: olesiabilkei/123RF Stock Photo

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