Goals of Prenatal Studies

Like any other study, prenatal examination at different stages of pregnancy has its goals. It is important to know that the specialist who performs it should be aware of these goals and explain them to his patients before the study. This article was provoked by false, incomplete and incompetent opinions that have been written and spoken in many places on the Internet space in Bulgaria. The reasons for this, I think, are ignorance of matter, financial interests, or is provoked by a distorted personal sense of justice. Unfortunately, there are many people who, without having the necessary knowledge, express a ‘convincing’ opinion.

Performing an ultrasound examination during pregnancy may be both routine and family-related, past or current maternal illness, genetic abnormality carriership, open fetal deviation, and so on.

For routine examinations, we accept examinations in 11-14 WOG, 18-22 WOG and 32 and/or 36 WOG. I believe that the reason for each of these examinations has been specified in the articles for the appropriate period of pregnancy, but I will still allow myself to describe the goals once more. All of these examinations are routine and should be performed on any pregnant woman to track the normal development of pregnancy, fetus, placenta, amniotic fluid and blood flow (Doppler study).

I start with the examination in first trimester or the one between 11-14 WOG. During this period of pregnancy, all organs and systems of the fetus are formed, from here onwards they follow their maturation. Until this period of pregnancy the risk of miscarriage was 15%, after 12 WOG is now only 2-3%. This should be a moment of relief for you, future mothers. Of course, you may still have morning nausea and vomiting, but if you do not have more than four to five times a day, not connected with eating, take enough liquids and manage to eat, though less, you need to be calm. Soon and morning nausea and vomiting will pass away. For those who have vaginal bleeding and morning nausea, do not worry, the fact that these are  two separate symptoms does not increase the risk of abortion, but it just reduces it. It is unclear why, in bleeding and nausea, the risk of abortion is lower, but is described in most textbooks and manuals. After the brief introduction/deviation, I begin with the reasons for performing a 11-14 WOG ultrasound examination. Before the examination, each doctor ‘takes’ a detailed history (questioning) of the patient. If you have not had another examination to date, which I doubt, but in the UK this is mostly the first examination, now is the time to determine the place and the number of fetuses. I.e. whether the pregnancy is singleton, bigeminal, triple, etc. In humans, the most common spontaneous pregnancy is singleton, rarely there is bigeminal, and extremely rarely multifetal pregnancy. With in vitro fertilization and embryo transfer of more than one embryo, the number of multifetal pregnancies increases. When multiple pregnancies occur, one should determine whether they share one placenta or have separate placentas. In the presence of multiple pregnancies with one placenta, the risk of complications of pregnancy is much greater and requires frequent follow-up. The next step is the presence of cardiac activity on each fetus. Every parent is excited to hear the throb of the heart of his child.

After determining the number of fetuses and heart activity, the placental location, a subjective assessment of the amniotic fluid should be determined. During this period of pregnancy, it is found to be the most accurate time to date the pregnancy and to tell you the term. Yes, that’s right, we will now measure the fetus and according to its size, we will determine how far the patient is gone in pregnancy. For this purpose, the fetus should be within a range between 45mm and 84mm. Once we give you the new term from here until the end of pregnancy, it will be our guide and will not change for any reason! Defining the term on the last menstrual period is not so accurate method, because even if you have a very regular period, few women know exactly when ovulation has occurred. Even if you are aware of the date of ovulation and the date of the sexual intercourse, it is also important to specify that the sperm life is between 24-48-72h, and the ovum 24-48h., i.e. the actual fertilization can be done with a difference of 2 to 3 days. And this is important in tracking pregnancy and fetal growth. The most accurate method for dating pregnancy is in in vitro fertilization and fresh transfer. Then we know the exact moment of fertilization and the date of the term has to be determined by the clinic in which the in vitro procedure was performed. Therefore, in patients with such pregnancy, we do not change the term and do not date.

Among the main objectives of the examination in the first trimester between 11-14 WOG is screening for the most common chromosomal abnormalities – Down, Patau and Edwards syndrome. Combined screening test is performed and the risk for each of these anomalies is calculated by the age of the woman, biochemical parameters from the blood test, and ultrasound markers and parameters.

And here comes the question why we need to examine if your child can have a Down syndrome!? The analysis, especially combined screening test, and cff DNA, are non-invasive procedures related only to taking venous blood from the pregnant woman. These methods do not pose a risk either to you or your baby. With these two methods, screening is also done for Patau and Edwards syndromes. Detecting some of these syndromes would be extremely helpful for both you as a prospective parent and for us, the medics. It is important for parents because they will be able to make the right decision for them – whether to continue pregnancy or discontinue it. I.e. the presence of any of these or other abnormalities in no way obliges you to commit an abortion! This decision is ONLY YOURS! We will support you in your choices with understanding, with more information and the follow-up medical activities dictated by you. If you do not want to have a child with some of these syndromes, the end of the first trimester is the most appropriate and poses the least hazards for you and your childbearing ability. If you decide to continue your pregnancy, you will become more aware of this condition, look for more information, and you will be far more prepared to take care of your child and what you will experience after birth. For us, doctors, it is important to be able to track pregnancy more closely, to look for anomalies in detail, to plan birth, and not least to give you advice on next pregnancies, to direct you to genetic counseling if necessary, to determine the risk of recurrence of this syndrome in the next pregnancy.

Another important objective of the examination in 11-14 wog is the trace of anatomy of the fetus in the early stages of pregnancy and detection of abnormalities. Yes, even in this early period, it is possible to detect multiple abnormalities.

Fetal morphology takes place between 19th and 22nd WOG. The aim of fetal morphology is to trace the normal anatomical and physiological development of the fetus for this period, to make biometric measurements, respectively to detect pathological changes, if any, to conclude and determine the follow-up. It is a highly specialized study done with a high-resolution echograph.

If we detect deviations during this period of pregnancy, we should ask ourselves the following questions: What is this anomaly? Is it related to other deviations? What are the consequences of this/these anomalies? Is this condition compatible with life? What is the severity of the anomaly? What can be the reasons? How can these reasons be detected? What can we do? What alternatives do we have? Once we answer all these questions together, we come to a decision on the follow-up and alternatives. In some severe anomalies, the possibility of interruption of pregnancy may be considered.

Fetal morphology is done until the 22nd WOG as long as there are serious anomalies within this time, there is a time up to 24 WOG until an abortion can be made on medical evidence. After this period, a medical abortion can only be performed in conditions that endanger the mother’s life.

Examination after 28 week of gestation or monitoring the growth of the fetus. The aim is to trace the dynamics of how the fetus grows, the sequence of the growth of the individual indicators, the relationship between them and the sequence as a whole. We look at the placenta again for position, structure and maturity. We measure the presence of amniotic fluid, maternal blood flow to the placenta, placenta to the fetus and blood flow of the fetus. We observe breathing movements, body movements and the limbs of your baby. All this shows us the viability of the fetus, the discovery of early signs of suffering of the fetus of different nature and the possibility of drawing up a follow-up plan.

Of course, within this period, we are doing biometric measurements of the fetus to track its growth. Deviations from the norm may be in one direction or another and signal a different pathology. It is important to trace not only whether it is in the norm but also the systemacity of growth, i.e. whether it follows one growth line or there are deviations from that line. A complete idea of growth needs to be built up to draw conclusions. If there are any deviations, the reasons are sought with further studies and more frequent tracing of the fetus with an echograph.


Center for Fetal Medicine

Get informed about the world of Fetal Medicine with Dr. Boris Stoilov.

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