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The Fetal anatomy scan - a modern trend or indisputable necessity?

Prof. Dr. Dimiter Markov


Prof. Dimiter Markov graduated from Medical Faculty of Sofia Medical University (SMU) in 1998. In 1999 he became a Ph.D. student at the Department of Obstetrics and Gynecology, SMU. In 2000 he started a two-year specialization in the Department of Prenatal Diagnosis lead by Dr. Philip Loquet at University Hospital of Antwerp (UZA), Belgium. From 2003 to 2012 he worked at University Hospital "Maichin Dom", Sofia. He has been a Professor of Obstetrics and Gynecology at the Facultyr of Public Health, SMU since 2015. He has performed over 60,000 ultrasound examinations and hundreds of invasive procedures under ultrasound guidance in the field of prenatal diagnosis.


Prof. Markov has been the manager of MC MARKOVS since 2007.


What is called "The fetal anomaly scan"?

The fetal anomaly scan is a comprehensive and highly specialized ultrasound examination performed in pregnancy during which all major fetal organs and systems are evaluated. Depending on the gestational age information regarding the fetal development and the pregnancy as a whole is obtained. In the course of the examination a number of measurements are taken (fetal biometry) and the gestational age with the probable due date are assessed. In addition, a systematic evaluation of the fetal anatomy is performed and various types of structural defects are excluded. At the same time, the risk of associated genetic abnormalities is assessed by analyzing multiple ultrasound markers. A Doppler examination of the maternal and fetal circulation, as well as an ultrasound screening for preterm delivery by measurement the cervical length are also performed. The location of the placenta and the amount of amniotic fluid are documented. After the examination is completed, a detailed written protocol is given with the established sonographic findings. Key to the study are the professional qualifications of the doctor and the qualities of the ultrasound equipment used.


Why do we talk about three fetal anomaly scans during pregnancy?

Examinations for the assessment of fetal morphology are three (in each trimester), because the fetus develops continuously during pregnancy. For example, in the first trimester the fetus is less than 100 grams, in the second it is about 300-400 grams, and in the third trimester it is over 1200 grams. It is practically impossible to exclude all structural defects in the prenatal life performing only a single exam. For these reasons, the ultrasound assessment of fetal morphology has its specificity in each of the different gestational periods.


The examination of fetal morphology between 11-13+6 w.g. (optimally 12-13+6 w.g.) focuses on determining the correct gestational age, excluding major fetal structural abnormalities, ultrasound screening for chromosomal abnormalities, and Doppler examination to assess maternal-fetal blood flow.


Fetal morphology between 18-23 w.g. (optimally 20-23 w.g) emphasizes on the careful examination of all organs and structures of the fetus - brain, face, heart, spine, abdomen, limbs, etc. In addition, ultrasound screening for chromosomal abnormalities of the fetus is also performed, as well as ultrasound screening for preterm birth by measuring the length of the cervix. A Doppler study of blood flow between mother and fetus is also usually indicated.


Fetal morphology between 28-32 w.g. (optimally 28-30 w.g.) is the third most important ultrasound examination during pregnancy. Through it, between 5 and 10% of structural anomalies possible for prenatal diagnosis are excluded - those with a later clinical manifestation. In addition, the rate of fetal growth and development is evaluated, as well as a Doppler examination of the fetal blood circulation. The localization of the placenta, the umbilical cord and the amount of amniotic fluid are again studied. Recommendations are given for the method of delivery.


What is the benefit of performing a fetal anatomy assessment?

The benefits of having a fetal morphology review performed by a qualified specialist are many. First of all, in the majority of cases, examination of fetal morphology brings peace of mind. Usually, after such an examination, it is found that the pregnancy is developing in the right way and everything is fine. Unfortunately, however, this is not always the case. In some cases, problems or complications are diagnosed in the course of the examination, which require refinement of behavior and making difficult decisions - whether to undertake additional tests and what, whether to continue with the development of the pregnancy at all and, if so, what to expect from the future... It is in such cases that the information obtained from the evaluation of the fetal morphology turns out to be invaluable. For me, the biggest benefit of this screening is that it gives expectant parents the right to make an informed choice.


Can the fetal anomaly scan do any harm?

The biggest harm from performing the sonographic assessment of fetal anatomy is the incorrect interpretation of what has been found during the examination. For example, in some cases, the clinical significance of an ultrasound finding may be unnecessarily exaggerated or, conversely, downplayed. In other cases, it may not be detected at all or may be misinterpreted or incorrectly explained. The balance is very delicate Regardless of the fact that everywhere in the large specialized centers for fetal morphology work using a protocol, in practice, the way the examination proceeds is strictly individual and depends to an exceptional extent on the qualifications of the doctor performing the examination. It is important to know that the way if consulting and presentation of the received information is also very important. When there is one and the same sonographic finding, the patient can leave the doctor's office very upset or completely relieved depending on the doctor's way of consultation, for example. 


What are the limitations of the fetal morphology scan?

Like any clinical method in medicine, the ultrasound evaluation of fetal morphology has its limitations. Essentially, the ultrasound examination is a way of prenatal diagnosis of the structural (anatomical) defects of the fetus. A certain part of them are subject to prenatal diagnosis in the different gestational periods. There are also structural defects, however, that cannot be diagnosed before birth. Unlike structural abnormalities that can be detected sonographically, genetic defects require other (genetic) tests to make an accurate prenatal diagnosis. For this reason, it is unrealistic to expect that fetal anatomy scan can correctly and accurately identify all cases of Down syndrome or all other genetic conditions, defects and syndromes that exist in nature. Another very important limitation of fetal morphology assessment is that the method is subjective and largely depends on the qualification of the specialist performing it.


What would you say in conclusion?

The ultrasound examination of the fetal anatomy plays a key role in modern prenatal care. In the majority of cases, its implementation brings peace and confidence to future parents. However, sometimes it identifies problems or potential risks for complications. This allows the prospective parents to make an informed decisions based on the objective analysis of the information received. The main limitation of the examination is its subjective nature, which makes it highly dependent on the qualifications of the examiner.