How many types of prenatal ultrasound are there and what do they indicate?
In previous posts, we have attempted to shed some light on one of the normal pregnancy tests with which you must now be familiar. But in an attempt to provide you with access to all information, we wanted to add to this documentation to tell you about the various types of ultrasound and what they indicate.
The use of the ultrasound encompasses a number of areas, such as the diagnosis and confirmation of teenage pregnancy. For instance, the gestational sac can be identified as early as four and a half weeks into the pregnancy. The embryo can be identified approximately five and a half weeks into the pregnancy. The ultrasound can also confirm one very important aspect: that the embryo has ‘nested’ within the uterine cavity. If this was not the case, we would have an “ectopic pregnancy”. There are several kinds of ultrasound:
Abdominal ultrasound: The first ever ultrasound to be used; it offers less resolution than the vaginal kind because abdominal fat gets in the way; having said that, it can also be used for pregnancies, although the images that are obtained are more difficult to see; for example, the gestational sac can only be seen one week after the period in which in becomes visible for the vaginal kind. This ultrasound is used at the end of the pregnancy.
Transvaginal ultrasound: this scan is performed by placing a probe into the patient’s vagina. By and large, this method provides better images (and therefore more information) in patients that, for instance, may be overweight or in the initial stages of the pregnancy. The foetal heart rate can be clearly identified as early as the sixth week of the pregnancy. These vaginal explorations are also becoming essential in the early diagnosis of ectopic pregnancies.
Two-dimensional or 2D ultrasound: This is the most commonly used form. Echoes ricocheted by structures crossing the ultrasound beam are visible as multiple sequential images in greyscale. As its name would suggest, it is two-dimensional and is shown on a monitor in real time, although the image will be blurred if the foetus is moving about. The monitor displays moving images in real time, they are flat and in black and white. The ultrasound printed on paper also shows a fixed and flat image in black and white or in greyscale.
3D ultrasound: it shows a clearer image of the baby and gives it volume. This kind of ultrasound has been used in gynaecology since the end of the 1980s and the beginning of the 90s; it has revolutionised the field of diagnostic imaging, as it offers a stunning resolution and definition of the foetus in relation to the standard two-dimensional ultrasound. That is why it is used in particular cases where details need to be seen, although the 2D ultrasound can generally detect defects or irregularities.
The 3D ultrasound is based on the same basic principle of any ultrasound, although it also includes the measurement of the foetal volume, unlike 2D ultrasounds. It shows us a static 3-dimensional image of the foetus and its structure using a sharper colour than the black and white of a standard ultrasound. High-tech equipment provides traceability and captures the image quickly, meaning that the three-dimensional image of the foetus is subsequently obtained, which is in turn recorded on the software of the data-processing equipment. Several operations are carried out instantly to obtain the 3D image.
Four-dimensional: this is cutting-edge technology; it is a video of the ultrasound of the foetus inside the mother’s womb. It is a 3D ultrasound although it is recorded and seen in real time. The image of the foetus that is displayed provides the highest quality and is the most life-like available: it shows actual movements and shows, for example, if the baby is sucking its finger, moving its head, yawning or playing with its umbilical cord…
The most suitable time to perform this scan is between week 25 and 32, as its movements and facial features can be better identified at this stage, although it should not be forgotten that it is usually undertaken in private hospitals.
However, it is important for parents-to-be to understand that the ultrasound has a margin for error in the detection of chromosomal abnormalities; this means that it does not provide an absolute guarantee and requires a number of different blood tests which, along with the ultrasound, provide a probability of the risk that the baby will be affected by these abnormalities. Furthermore, the emergence of the Nace Test should be taken into consideration; this is a blood test of the mother which is capable of detecting the most common chromosomal abnormalities, such asDown’s Syndrome, Edwards’ Syndrome and Patau’s Syndrome. The advent of this new test gives hope to many future parents.