At what stage of pregnancy should you have an ultrasound? About Down syndrome. About Doppler studies.
Can ultrasound be harmful?
Ultrasound is the basis for detecting all kinds of fetal malformations, as well as a very reliable and inexpensive way to monitor the baby.
Scientists have proven that no matter at what stage of pregnancy an ultrasound is performed in the ordinary (so-called B-mode), it is absolutely harmless to the baby. This procedure can be performed several times during pregnancy.
During an ultrasound examination you are exposed to high-frequency waves, usually in the range of 3.5-5 MHz. These waves have nothing to do with radioactivity; they are sound vibrations whose frequency spectrum lies beyond our hearing. The ultrasound wave that is sent out is reflected from various body tissues and picked up by a special device. All of this resembles an echo in the mountains and is called echolocation.
The large number of ultrasound examinations that most expectant mothers undergo, by and large, cause no harm, but at the same time they provide no additional information about the fetus, so for the most part they are pointless. Leading manufacturers of ultrasound equipment and leading clinics follow the ALARA principle (AS LOW AS REASONABLY ACHIEVABLE), "as little as necessary", when performing ultrasound examinations. That is, the power parameters of the device's sound signal are kept within a safe range. We fully support this principle.
An examination for the sake of an examination can be called foolish, because everything done when examining young mothers must follow the principle of "do no harm" and aim at making an accurate diagnosis.
At what stage is ultrasound done to get the most information?
The optimal times for ultrasound (ultrasound examination) are 12–14 weeks, 21–24 weeks and 32–34 weeks.
An ultrasound examination at 12–14 weeks makes it possible to identify the so-called risk group, in which there is a likelihood of having a baby with various defects, abnormalities in the structure and number of chromosomes, and similar conditions.
The timing of the ultrasound is linked to the ability to detect characteristic signs that are absent before 11–12 weeks and disappear after 14 weeks. The presence of these signs does not yet mean that a diagnosis has been established.
In addition, at this stage it becomes possible to determine the gestational age more accurately, establish the features of the placenta and detect the most obvious defects.
The 2nd examination (21–24 weeks) is prescribed to assess the anatomy of the fetus. This is the optimal time to see the baby's features in detail.
Examinations at 16 to 19 weeks performed on mid-range ultrasound machines, as well as on outdated models, can easily create all the preconditions for poor-quality and delayed diagnosis of many defects or even serious diagnostic errors.
It is important to know that the laws of body physics mean that not all deviations from the normal development of the baby in the womb can be detected by ultrasound, even at twenty-one to twenty-four weeks. Some developmental features appear at later stages or even after the baby is born.
Any change in the timing of ultrasound reduces the effectiveness and benefit of this procedure.
The accuracy of an ultrasound depends on the professionalism of the attending doctor, how modern and expensive the equipment is, as well as on the number of fetuses, their position relative to each other, whether the young mother has obesity, and other factors.
The 3rd examination (32–34 weeks) is used to detect abnormalities that appear at later stages. At 32–34 weeks, additional procedures are performed (Doppler ultrasound, cardiotocography), which have their own indications and are aimed at assessing the condition of the fetus in the womb and predicting (forecasting) possible complications during pregnancy and childbirth.
Ultrasound question: what abnormalities can be detected by ultrasound at different stages?
The standard ultrasound examination protocol includes a step-by-step examination of the fetal organs and systems that are subject to examination using ultrasound waves. It follows that only gross anatomical abnormalities are accessible to ultrasound diagnostics. Changes in small organs and minor defects cannot always be detected by ultrasound.
Even today, the greatest difficulties are associated with diagnosing heart defects in the fetus.
Remember! Ultrasound is extremely informative, but it has certain limits of what is possible and cannot solve absolutely all problems.
Down syndrome.
Down syndrome is a fairly common chromosomal abnormality. Among newborns, the risk of Down syndrome occurs at a rate of 1 in 800 children. Like other chromosomal syndromes, Down syndrome occurs randomly and cannot be treated. At the initial stage of the disease, it may cause delayed mental development in the child, accompanied by developmental abnormalities. Down syndrome is also associated with metabolic disorders and immune disorders.
This diagnosis can be made only through laboratory analysis of material obtained during an invasive test. That is, when there is a risk of Down syndrome, a puncture through the mother's abdomen (amniocentesis) must be performed to collect placental cells, amniotic fluid or fetal blood. Analysis of this material makes it possible to establish the chromosome set and diagnose chromosomal disorders in the fetus in 100% of cases.
An invasive test can sometimes lead to pregnancy loss, so it cannot be performed on absolutely all women. Among all mothers, those with an increased risk of having a baby with abnormalities need to be identified.
It must be noted once again that the disease can appear randomly in healthy families where no one has had it before.
Ultrasound, no matter at what stage it is performed, cannot detect "abnormalities in the child's mental development". Ultrasound (both 2D and 3D) helps identify chromosomal markers, such as the thickness of the "nuchal zone", the length of the nasal bone, and others.
Factors that increase the risk of a child developing a chromosomal disease include:
- changes in the structure of chromosomes in one of the spouses;
- certain signs detected on ultrasound;
- mother's age over 35;
- abnormal levels of AFP, hCG, PAPP-A in the mother's blood;
- previous birth of a child with Down syndrome.
Ultrasound examination does not make it possible to diagnose Down syndrome! This method only makes it possible to suspect it.
Nevertheless, identifying and detecting Down syndrome is generally a difficult task. Unfortunately, at present no less than fifty percent of cases of this syndrome are missed during pregnancy and are detected only after birth.
To increase the effectiveness of Down syndrome diagnosis and reduce the likelihood of undesirable development of the disease, ultrasound examinations should be performed at twelve to fourteen weeks. This will make it possible to accurately identify the risk group and take measures in time.
What is an invasive test and how does it differ from ultrasound?
An invasive test is a puncture of the amniotic cavity performed through the anterior abdominal wall under ultrasound guidance. Its purpose is to obtain material for further examination of the chromosome set, as well as examination of certain genes.
This procedure is used only when there are strict medical indications, because the risk of pregnancy loss is approximately 2% out of 100.
In all cases (except when there is a threat of miscarriage), this medical procedure does not require hospitalization of the patient.
Doppler studies. Indications and definition.
A Doppler study is an examination of the volume and intensity of blood flow in the vessels of the baby, the placenta, the umbilical cord and the mother's uterine vessels. These studies are performed on ordinary ultrasound machines equipped with special modules for this purpose. They are combined with standard ultrasound examinations.
The results of this method provide information about the state of blood flow and indicate the condition of the fetus. At later stages, after 30 weeks, Doppler ultrasound becomes a desirable component of any ultrasound examination.
Indications for which a Doppler ultrasound is prescribed:
- fetal size not corresponding to gestational age;
- maternal diseases (diabetes mellitus, abnormal blood pressure, kidney disease);
- abnormal volume of amniotic fluid, premature maturation of the placenta, etc.
Remember! Good blood flow indicators on a Doppler study are among the reliable signs of normal fetal development, but they do not rule out various complications at later stages. Fetal blood flow disorders require especially careful monitoring, including in a hospital setting.
