Use of Ultrasound during Pregnancy

3D UltrasoundOne of the most commonly thought of uses for ultrasound is the scans during pregnancy. These have many uses, not only are they for medical purposes such as diagnosing abnormalities and keeping track of fetal growth, it also has massive benefits for the mother to be. Ultrasound scans are often approached with enthusiasm and excitement by the parents, as it contains many baby lifetime firsts. Whether it is the first time a mother hears her child’s heartbeat, the first time she sees its face or even the day she discovers the baby’s gender. This article is aimed at 2 groups of people, firstly parents who are looking to find out more information about the ultrasound they are about to receive, details on what happens during the different stages of development and what you can expect to see at your ultrasound depending on how many weeks pregnant you are at the time of your scheduled appointment. This can also be useful if you are looking forward to a particular “first” and want to find out when this can happen. It will also be beneficial for ultrasound technicians who are interested in specializing in obstetric ultrasound as it gives a basic overview of the different stages of development you will be facing during training.

A brief overview of ultrasound

Obstetric ultrasound is the use of ultrasound during pregnancy; this includes the more traditional 2D ultrasound scans, as well as the recent innovations of 3D and 4D ultrasound imaging. Ultrasound works by sending out sound waves which operate at a higher frequency than that of human hearing (about 20,000 hertz). The sonographer uses a small hand held device called a transducer, which sends out and receives the ultrasound waves. These sound waves bounce off of the internal structures of a body, and produce echoes which are picked up by the transducer. The ultrasound machine can then process the time it took for this echo to return, and from that work out the distance travelled; it then combines all of these signals and distances into a single image or sonogram.

Is ultrasound safe?

There is absolutely no evidence of any kind that ultrasound can do any harm to a person or baby.  Even so extra care is taken with obstetric ultrasound machines, such as limiting their power output, this is done on a “just in case” basis to make sure both mother and child are given the best possible treatment.

Stages of Development – Significant Events

It is probably best to say here that the dates and times below are generalizations based on “normal” experiences. Every person and every pregnancy is unique, just because the times below are listed does not mean that if yours does not follow them exactly there is anything wrong. Although most people will follow this order and timing, they are not set in stone. Below you will find an ultrasound video featuring a 12 week old baby, it shows off various angles in 2D ultrasound including descriptive notations and heartbeat audio!


One of the first milestones for baby ultrasound imaging is that of the heartbeat. The first time a mother hears her baby’s heart beat can be a truly emotional and motivating experience, many look forward to this ultrasound scan and the resulting baby pictures.

When is the earliest an ultrasound scan can detect a baby’s heartbeat?

Around the 5 week period following conception is when a baby’s heart is formed enough that it starts to beat. At this point in time however, it is far too weak to produce sound waves of significant enough strength to be detected, even after being magnified via medical equipment. The first time there is a possible chance to hear the heartbeat is at 8 or 9 weeks, during this period it begins to be possible to detect the heartbeat via ultrasound; however it is common at this early stage to find that the heartbeat is either faint or inconsistent. By 12 weeks old development of the heart has advanced significantly and an ultrasound scan should be able to readily detect the heartbeat.

Gender Determination

Although it is not the wish of every parent, there is an increasing desire among parents to discover the sex of their child before the actual birth. The advantages of this are increased time to plan and build ready for the “big day”, while also allowing thought about the name of the baby without having to decide on two different names. Although it is theoretically possible to determine the sex of a baby at 12 weeks, it is not recommended nor would it be particularly accurate at this early stage. In fact hospitals regularly refuse to determine the sex of a child until the 20 week period, this is due to the fact that by this time it is relatively easy and reliable to find out what the sex is and they do not wish to waste resources unless there is a medical reason to do so. To fill the niche that this leaves of parents that wish to know their baby’s gender but do not wish to wait until the 20 week period, 3D ultrasound centers have been created. These centers have roughly a 50% accuracy rate at 15 weeks although the reliability of any judgment this early in development is questionable, however by 16 weeks this has risen dramatically to a 99% reliability and accuracy rating.

3d ultrasound scan and modeling3D Ultrasound

3D and 4D ultrasound is a recent innovation that is loved by sonographers and parents alike. Not only does it allow clearer more detailed images, but allows parents to really see their child without having to have the picture explained, the image looks like a “real” baby. Besides the obvious medical benefits of clearer imaging, there are also real advantages for the parents including improved bonding between mother and child. It is for this reason mums approach a 3D ultrasound appointment with such excitement. There are two main questions I have come across from expectant mothers who are looking for information about 3D ultrasound.

How soon can I have a 3D ultrasound?

The earliest you can undergo a 3D ultrasound is 17 weeks if you follow the recommended advice. Although you could theoretically have this procedure earlier, 17 weeks is the desirable minimum due to possible negative exposure effects it can have on the mother. The clarity of this imaging technique is astounding, which can also count against it early on in fetal development. The reason for this is that if the mother sees her baby too early in a 3D environment it can actually harm the bond between them as the baby can seem alien or not like a “real” baby. After 17 weeks however, the baby has developed enough to be recognizable, and therefor produce the images all mothers dream about showing around at work.

When is the best time to have a 3D or 4D ultrasound?

If you are after really nice, high quality baby ultrasound pictures then you should try to arrange for an appointment between 24-32 weeks, ideally within the 26-28 week period. The reason for this is that at this time the baby is still small enough to get a great baby image, and is still in the correct position in order to obtain it. After the 32 week period there is an increasing chance that the baby will have descended into the pelvis, after this happens it is nigh on impossible to achieve the level of detail that a mother desires.


Just to round it off and because we all love a good baby photo, below is a collection of baby ultrasound pictures both 2D and 3D. For a later article we will include a gallery of ultrasound images that show pregnancy week by week to further demonstrate the developmental stages of fetal growth.

9.5 Weeks

9 Weeks 5 Days – Courtesy of Abby Batchelder


12 week old 2D ultrasound

12.5 Weeks – Courtesy of Michael Quinn

3D ultrasound to real life comparison

Courtesy of Andy Wana

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