Examination of a baby deformed in the womb, not a ‘magic wand’

All pregnant women pay much attention to whether the baby is healthy or not. As the fertility rate has recently decreased, each baby receives more attention and expectations, and this trend seems to intensify.

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Therefore, pregnant women often visit obstetrics and gynecology hospitals to check the health of their baby and do various tests. Among these tests, the most frequently mentioned is the so-called ‘diagnostic deformity test’. The term ‘deformation screening’ is a very broad and ambiguous term. So, what is ‘malformation’ and what causes it to be named this way? ‘Anomaly’ is a term with the meaning of ‘an abnormality in the structure-appearance, etc., that occurs during the ontogenesis of an organism’, and its causes include genetic influences, hormonal abnormalities, nutritional abnormalities, viruses, radiation, other microorganisms, trauma, etc. There is this.

So, what is a ‘diagnosed child’s inspection’ in general? The exact expression can be called ‘maternal serum screening test’. Maternal serum refers to the blood of pregnant women, and screening test means to estimate the frequency of occurrence of any disease. In other words, it is a test that estimates the frequency of occurrence of diseases by analyzing certain components in the blood of pregnant women, which means that the disease is a deformed baby.

However, in actual maternal serum screening test, the diseases selected are not all causes of birth defects, but three diseases. The first is trisomy 21, a disease commonly referred to as Down’s syndrome, meaning that there are three chromosomes 21 instead of two among humans. The second is trisomy 18, which is Edwards syndrome with three chromosomes 18. The third is neural tube defect, which refers to a situation in which the fetal neural tube is not completely closed and partially open, so the membrane surrounding the spinal nerve or part of the nerve protrudes out of the skin of the lower back. Now, if you write the ‘deformation test’ correctly again, it will be like this. ‘A test to estimate fetal trisomy 21, trisomy 18, and neural tube defects by obtaining mother’s blood in the first half of pregnancy and analyzing certain components of it’

With this explanation, you will be asked the following two questions most often: Then, why is it not included in the screening test if there is only one chromosome 5 or if there are three chromosome 19?

The main reason for this is that the main purpose of this test is to select mainly cases where pregnancy is maintained well and leads to childbirth. Therefore, other chromosomal abnormalities, which have a low incidence or are often aborted spontaneously, are of low importance for screening.

Trisomy 21, trisomy 18, and neural tube defects have a relatively high incidence and a low rate of miscarriage during pregnancy. More importantly, newborns with this disease are at a very high risk of experiencing difficulties such as breathing difficulties and heart problems at birth. For this reason, special attention of medical staff is required during childbirth, and various medical equipment is required in advance to speed up measures to help the baby’s breathing and survival immediately after birth. In addition, there is a secondary purpose of helping families to know the baby’s disease in advance and to build up knowledge for raising a baby in advance.

The second question is ‘what is the accuracy of the malformation test, and if the test is positive, does the fetus really have the disease?’

Many readers of this article will already know the answer. Screening tests do not give a correct answer, but give the result of a risk analysis of low or high risk and a number such as 1:500.

This number means that if you have these results, you will have the disease at a rate of 1 in 500 people.

In addition, the risk grouping result also has a ratio of false-positive (when the test result is positive but there is no disease) and false-negative (when the test result is negative but actually has a disease), so it is quite difficult to understand this result accurately. It’s difficult.

In fact, at Seoul St. Mary’s Hospital, there are many cases where normal chromosomes were confirmed through amniocentesis in mothers who were at high risk for trisomy 21 (Down syndrome).

Usually, amniocentesis test takes about 10 days to 2 weeks, so in this case, the fluorescent in situ matching test, which identifies only the number of chromosome 21 before chromosome analysis, will inform you of the results in one day. It’s such an important test that I get nervous every time I check and read it, and I double-check it a few times before reporting it.

Because the amniotic fluid test serves as a confirmatory test to discriminate between false positives and true positives, it is explained that additional tests are necessary depending on the results before screening.

So how do we detect false negatives? Another important test that supplements this is ultrasound. The obstetrician can determine the need for amniocentesis by accurately evaluating the growth rate of the fetus according to the gestational weeks, the proportions of the body, and the development of various organs through ultrasound examination. There are also studies that show that the most common chromosomal abnormalities are

So far, maternal serum screening has been mainly described, but this also applies to ‘fetal DNA testing’. The fetal DNA test has improved accuracy than the screening test used so far, but it also reports the results only at risk, and the risk of false positives and false negatives still remains. Among the diseases mentioned above, neural tube defects cannot be detected by this test.

Tests to check the health of the fetus are becoming more and more developed. In this case, it is necessary to fully understand and implement the method, content, and interpretation before undergoing the examination.

An obstetrician I know explains this before the examination. ‘Just as crucian carp does not contain crucian bungeoppang, a malformation test is not a magic wand that can test for all malformations in the fetus’.

It may seem very complicated after organizing it like this, but in fact, it can be relatively easy to explain the situation each person is in. If you have any questions or want to confirm, ask questions and discuss with your obstetrician or genetic diagnosis and testing center, and we expect that you will know more clearly and come up with a countermeasure to get the best results.

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