One of the most exciting moments for a woman during the period of bearing a child is screening for congenital fetal pathologies. They are held for all pregnant women, but not every expectant mother is told in detail and explained what kind of research it is and what it is based on.
In this regard, screenings are overgrown with a mass of prejudices, some women even refuse to undergo procedures so as not to “waste their nerves”. We will tell you about what this diagnostic is in this article.
What it is
Screening is sifting, selection, sorting. This is the meaning of this English word, and it fully reflects the essence of the diagnosis. Prenatal screening is a set of studies that allow calculate the risks of genetic pathologies.
It is important to understand that no one can claim on the basis of screening that a woman is carrying a sick child, the screening results do not report this.
They only show how high the risk of having a given woman is given her age, history, bad habits, etc., of a child with genetic abnormalities.
Prenatal pregnancy screening has been introduced at the national level and became mandatory over two decades ago. During this time, it was possible to significantly reduce the number of children born with gross malformations, and prenatal diagnostics played an important role in this.
The terms in which these studies are carried out give a woman the opportunity to terminate the pregnancy if an unfavorable prognosis is confirmed, or to leave and give birth to a child with a pathology, but do it quite consciously.
It is not wise to be afraid of screening or refuse to undergo it. After all, the results of this simple and painless study are not binding.
If they are within the normal range, this only confirms that the child is doing well, and the mother can be calm.
If a woman, according to the test results, falls into a risk group, this does not mean that her baby is sick, but it may be the basis for additional research, which in turn can show with 100% probability the presence or absence of congenital pathology.
Screening is carried out free of charge, in any antenatal clinic, at certain stages of pregnancy. Recently, when pregnancy after 30 or 35 years is not at all considered a phenomenon out of the ordinary, such a study is of particular importance, because with age, and this is no secret, the age-related risks of giving birth to a baby with anomalies also increase.
What risks are calculated?
Of course, no medical technique is able to foresee all possible pathologies that a child may have. Prenatal screenings are no exception. Research only calculates the likelihood of a child having one of the following pathologies.
Down Syndrome
This is a congenital change in the number of chromosomes, in which 47 chromosomes are present in the karyotype instead of 46. An extra chromosome is observed in 21 pairs.
The syndrome has a number of characteristic features that a child is endowed with - a flattened face, a shortened skull, a flat nape, shorter limbs, a wide and short neck.
In 40% of cases, such children are born with congenital heart defects, in 30% - with strabismus. Such children are called "sunny" because they are never aggressive, they are kind and very affectionate.
Pathology is not at all as rare as it is commonly thought.
Before the introduction of screening, it occurred in one in 700 newborns. After screening became ubiquitous, and women were able to decide whether to leave a child with this syndrome, the number of "sunny" babies decreased - now there are more than 1200 healthy children for one such newborn.
Geneticists have proven a direct link between the mother's age and the likelihood of Down syndrome in a child:
- a girl at 23 years old can have such a baby with a probability of 1: 1563;
- a woman of 28-29 years old has a 1: 1000 probability of having a "sunny" child;
- if the mother is over 35 years old, but not yet 39 years old, then the risk is already 1: 214;
- in a 45-year-old pregnant woman, this risk, alas, is 1: 19. That is, out of 19 women at this age, one gives birth to a child with Down syndrome.
Edwards syndrome
Severe congenital malformation associated with trisomy 18 is less common than Down syndrome. On average, one in 3000 babies could theoretically be born with such an anomaly.
In late-bearing women (after 45 years), this risk is approximately 0.6-0.7%. More often, pathology occurs in female fetuses. The risk of having such a baby is higher in women with diabetes.
Such babies are born on time, but with a low (about 2 kg) weight. Usually, babies with this syndrome have a changed skull, facial structure. They have a very small lower jaw, small mouth, narrow small eyes, misshapen ears - an earlobe and tragus may be missing.
The ear canal is also not always there, but even if it is, then it is greatly narrowed. Almost all children have an anomaly of the foot structure of the "rocking chair" type, more than 60% have congenital heart defects. All children have a cerebellar anomaly, severe mental retardation, and a tendency to seizures.
Such kids do not live long - more than half do not live up to 3 months. Only 5-6% of children can live up to a year, rare units who survive after a year suffer from severe uncorrected oligophrenia.
Anencephaly
These are neural tube defects that can occur under the influence of adverse factors in the very early stages of pregnancy (between 3 and 4 weeks). As a result, the fetus may be underdeveloped or even absent from the cerebral hemispheres, and the vaults of the skull may be absent.
The mortality rate from such a defect is 100%., half of the children die in utero, the second half can be born, but only six of these crumbs out of a dozen manage to live at least a couple of hours. And only a few manage to live for about a week.
This pathology is more common in multiple pregnancies, when one of the twins develops at the expense of the other. The most common anomalies are girls.
The defect occurs on average in one case per 10 thousand births.
Cornelia de Lange syndrome
This ailment is considered hereditary, occurs in one case in 10 thousand births. It manifests itself as severe mental retardation and numerous developmental defects.
In such children, the skull is shortened, the facial features are distorted, the auricles are deformed, there are problems with vision and hearing, the limbs are short, and the fingers are often missing.
In most cases, babies also have malformations of internal organs - heart, kidneys, genitals. In 80% of cases, children are imbeciles, they are not even capable of simple mental activity, often they mutilate themselves, because do not control motor activity at all.
Smith-Lemli-Opitz Syndrome
This disease is associated with a congenital lack of the enzyme 7-dehydrocholesterol reductase, which provides the formation of cholesterol, which is necessary for all living cells in the body.
If the form is mild, symptoms may be limited to minor mental and physical impairments; in severe forms, complex defects and profound mental retardation are possible.
Most often, such babies are born with microcephaly, autism, with defects of the heart, lungs, kidneys, digestive organs, hearing and vision impairments, severe immunodeficiency, and bone curvature.
Every thirtieth adult on the planet is a carrier of this disease, but the “defective” DHCR7 gene is not always passed on to offspring, only one in 20 thousand babies can be born with this syndrome.
However, the alarming number of carriers forced doctors to include this syndrome in the definition of markers in prenatal screenings.
Patau syndrome
This is a genetic pathology associated with an extra 13 chromosome. It occurs on average once every 10 thousand births. The likelihood of a baby with such a pathology is higher in "age" mothers. In half of all cases, this pregnancy is accompanied by polyhydramnios.
Children are born small (from 2 to 2.5 kg), they have a decrease in the size of the brain, multiple pathologies of the central nervous system, anomalies in the development of the eyes, ears, face, cleft, cyclopia (one eye in the middle of the forehead).
Almost all children have heart defects, several additional spleens, congenital hernia with prolapse of most of the internal organs into the abdominal wall.
Nine out of ten babies with Patau syndrome die before they reach the age of one. About 2% of survivors can live to be 5-7 years old. They suffer from deep idiocy, are not aware of what is happening, are not capable of elementary mental actions.
Non-molar triplodia
An increase in the number of pairs of chromosomes at any level may be associated with a "mistake" during conception, if, for example, not one, but two spermatozoa entered the egg, and each brought 23 pairs of chromosomes.
In combination with maternal genetics, the child does not have 46 chromosomes, but 69 or another number. These children usually die in utero. Those born die within several hours or days, since multiple vices, external and internal, are incompatible with life.
This is not a hereditary disease, it occurs by chance. And with the next pregnancy, the chances of repeating the negative experience are minimal for the same parents. Prenatal screening can also predict the possible risks of such a pathology.
All of the above pathologies, if their risk is high according to the results of screening and if they are confirmed as a result of an additional examination, which is prescribed because a woman is at risk, are grounds for terminating a pregnancy for medical reasons at any time.
Nobody will be forced to have an abortion or artificial childbirth, the decision to terminate the termination remains with the pregnant woman.
Diagnostic methods
Prenatal screening methods are simple. They include:
- ultrasound examination, which, based on some characteristic markers, makes it possible to judge the possible presence of pathology;
- a biochemical blood test from a vein, in which the concentrations of certain substances and hormones are detected, certain values of which are characteristic of certain congenital anomalies.
There are three screenings for pregnancy:
- the first is always appointed for a period of 11-13 weeks;
- the second is carried out between 16 and 18 weeks;
- the third can be held from 32 to 34 weeks, but in some consultations these terms are more loyal - from 30 to 36 weeks.
For whom is screening required?
For all registered pregnant women, screening tests are routine and desirable. But no one can oblige a woman to donate blood from a vein and do an ultrasound scan as part of prenatal diagnostics - this is voluntary.
Therefore, every woman should think carefully first of all the consequences of her refusal from such a simple and safe procedure.
First of all, screening is recommended for the following categories of pregnant women:
- expectant mothers who wanted to give birth to a child after 35 years (it does not matter what kind of child it is);
- pregnant women who have already had children with congenital defects, including those with chromosomal abnormalities, have had cases of intrauterine fetal death due to genetic disorders in the baby;
- pregnant women who previously had two or more miscarriages in a row;
- women who took medications, medications that should not be used during pregnancy, in the early stages of fetal development (up to 13 weeks). These drugs include hormonal drugs, antibiotics, some psychostimulants and other medications;
- women who conceive a baby as a result of incest (ties with a close blood relative - father, brother, son, etc.);
- expectant mothers who were exposed to radiation shortly before conception, as well as those whose sexual partners were exposed to such radiation;
- pregnant women who have relatives with genetic disorders in the family, as well as in the event that such relatives are available from the future father of the child;
- expectant mothers who are carrying a child whose paternity has not been established, for example, conceived through IVF with the use of donor sperm.
Study description - how the screening proceeds
It is impossible to call prenatal screening an accurate study, because it reveals only the likelihood of pathology, but not its presence. Therefore, a woman should know that the markers on which the laboratory assistants and the computer program that calculates the probability can be found in her blood not only because of pathologies in the child.
So, the concentration of some hormones is increased or decreased as a result of the simplest colds, ARVI, food poisoning, which the pregnant woman suffered on the eve of the study.
Indicators may be affected lack of sleep, smoking, severe stress... If such facts take place, a woman must definitely notify her doctor about this in consultation before she receives a referral for screening.
Each of the screenings should preferably take place in one day, that is, both blood from a vein for biochemical examination, and a visit to an ultrasound diagnostic room should take place with a minimum time difference.
The results will be more accurate if a woman goes for an ultrasound scan immediately after she donates blood for analysis. The results are complementary; ultrasound and blood test data are not considered separately.
First screening and interpretation of its results
This screening is also called 1st trimester screening. The optimal time for it is 11-13 weeks.
In a number of antenatal clinics, the timing may vary slightly. So, it is allowed to take the test at 10 full weeks, at 11 weeks, as well as at 13 full weeks before the obstetric period of 13 weeks and 6 days.
Screening begins with the fact that the woman is weighed, her height is measured, and all the diagnostically important information that is needed to calculate the risks is entered in a special form. The more such information is indicated, the higher the accuracy of the study.
The end result is still produced by a computer program devoid of feelings and emotions, unbiased, and therefore the human factor is important here only at the preparatory stage - collecting and processing information.
The following are considered important for diagnosis: the age of the parents, especially the mother, her weight, the presence of chronic diseases (diabetes, pathologies of the heart, kidneys), hereditary diseases, the number of pregnancies, childbirth, miscarriages and abortions, bad habits (smoking, drinking alcohol or drugs), the presence of future mothers and dads of relatives with hereditary ailments, genetic pathologies.
The first screening is considered the most important of the three. He gives the most complete picture of the health and development of the baby.
In the ultrasound diagnostics room, the woman is waiting for the most common ultrasound, which she probably already did to confirm the fact of the pregnancy.
Ultrasound as part of a screening study is looked at:
- The physique of the crumbs - are all the limbs present, are they correctly located.If desired, the diagnostician can even count the fingers on the baby's arms.
- The presence of internal organs - heart, kidneys.
- OG - fetal head circumference. This is a diagnostically important indicator that makes it possible to judge the correct formation of the brain lobes.
- CTE - the distance from the coccyx to the crown. Allows you to judge the growth rate of the child, as well as to clarify the gestational age with an accuracy of the day.
- LZR - the frontal-occipital size of the fetus.
- Heart rate is the heart rate of the crumbs, the diagnostician also notes whether the heart contractions are rhythmic.
- The size and location of the placenta, the place of attachment.
- The number and condition of the umbilical cord vessels (some genetic pathologies can be manifested by a decrease in the number of vessels).
- TVP is the main marker that allows us to judge the likelihood of the most common pathology - Down syndrome, as well as some other developmental anomalies (Edwards syndrome, Turner syndrome, pathology of the structure of bones, heart.
The collar space is the distance from the skin to the muscles and ligaments at the back of the fetus's neck.
TBP is measured in millimeters, and the thickening of this skin fold, which is characteristic of children with chromosomal disorders and developmental defects, is undesirable.
TBP rates for first trimester screening:
Thus, if a child has TVP at 12 weeks higher than normal values, moreover, not by tenths of a millimeter, but much more, then ultrasound is prescribed again after a week or two.
A slight excess of the norm does not always indicate a pathology in a child. So, according to statistics, the diagnosis of "Down syndrome" in 12% of cases was confirmed with TVP at 13 weeks at 3.3-3.5 mm, and in women whose fetal TB was 2.8 mm instead of the normal 2.5 mm, disappointing diagnosis was confirmed only in 3% of cases.
Exceeding the norm by 8 mm from the upper border and more is an indirect indication of the likelihood of the presence of Turner syndrome, an increase of 2.5 - 3 mm may be a sign indicating the likelihood of the presence of pathologies such as Down syndrome, Edwards syndrome, and Patau syndrome. After 14 weeks, TBP is not measurable and has no diagnostic value. Laboratory data should complement the picture.
In addition to TVP, the diagnostician will certainly be regarded as an informative indicator of CTE (coccygeal-parietal size).
CTE norms at the first screening:
A very important marker of ultrasound examination of the first trimester screening is considered determination of the nasal bone in the fetus. Its absence (flattening) is characteristic of many congenital genetic pathologies.
The greatest experiences of expectant mothers are associated with this very bone, because not every pregnant woman has the opportunity to examine it and measure it. If the baby is located with his face inward, with his back to the ultrasound sensor, then you will have to try to force the baby to roll over, if this does not work, the doctor will put a dash or write that it was not possible to measure the nasal bones.
Usually, the norms regarding this marker are rather arbitrary, because there are people with large noses, and there are people with small snub-nosed "buttons". This congenital "nose" can theoretically already be seen on ultrasound during the first screening. And a small nose may well turn out to be a hereditary trait, and not a sign of malformations.
Therefore, it is good if at the first examination the nose is already located, it is visible to the doctor.
If not, then you should not get upset, you can repeat the ultrasound in a couple of weeks or visit another specialist, because different people can see something or not see it in different ways, not to mention the fact that ultrasound in different clinics is done on different machines level.
The size of the nasal bones (normal):
The blood test for the first trimester screening is called the double test because it measures the concentration two extremely important substances:
- PAPP-A - plasma protein, which is determined only in pregnant women;
- HCG, or rather β-hCG - human chorionic gonadotropin, the so-called pregnancy hormone.
The norms of hCG for a period of 10 to 14 weeks range from 0.5 to 2.0 MoM.
An increase in blood β-hCG may be an indirect sign of Down syndrome in a child, and a significant decrease in the level of this hormone may be a sign of Edwards syndrome.
An elevated level of hCG may be in case of multiple pregnancies in completely healthy children, in an overweight pregnant woman, with a history of diabetes mellitus, as well as in gestosis during pregnancy, accompanied by edema, high blood pressure.
Low hCG may also be due to the threat of miscarriage, if this woman has it, as well as with a delay in the development of crumbs, which may be accompanied by placental insufficiency.
Plasma protein norms - PAPP-A protein:
- at 11 weeks of gestation - 0.46-3.73 IU / ml;
- at week 12 - 0.79-4.76 IU / ml;
- at week 13 - 1.03-6.01 honey / ml;
- at 14 weeks of gestation - 1.47-8.54 IU / ml.
Since different laboratories use different reagents, working methods, then the readings in two different laboratories, if a woman donates blood in both on the same day, may differ from each other. Therefore, it is customary, as in the case of hCG, to determine the concentration of a substance in MoM.
The norm of PAPP-A for the first trimester is considered to be an indicator that is in the range of 0.5-2.0 MoM.
A decrease in the level of PAPP-A is regarded as a marker of the risk of Edwards syndrome and Down syndrome, Patau. Also, a decrease in protein may indicate the death of the baby in utero, about his hypotrophy with insufficient placental nutrition.
An increase in the level of PAPP-A should not cause concern if all other markers detected as a result of screening (TVP, hCG are within the normal range).
If the doctor claims that the expectant mother has an increased level of PAPP-A, this may indicate that the placenta in such a woman may be located low, that she has not one, but two or three babies, as well as that her baby is very well-fed, his parameters exceed age. Sometimes an increase in the level of this plasma protein indicates an increased thickness of the placenta.
A woman usually learns the results of screening in a few days or weeks. It all depends on how the accredited laboratory works in the region, how long the queue is.
To make it easier to understand what is happening, obstetricians-gynecologists try not to load the expectant mother with numbers, shares and MoM, they simply say that everything is in order or that additional research is needed.
The finished form of the first prenatal screening looks like a graph with explanations, just below - a computer program that summarized all the data about the woman and her health, the results of ultrasound and the concentration of hCG and PAPP-A, gives risks.
For example, Down syndrome - 1: 1546. This means that the risk is low, with the child, most likely, everything is fine. If the risk is designated as 1: 15 or 1: 30, then the probability of having a sick baby is high, more detailed diagnostics are needed to establish the truth.
Second screening and interpretation of its results
The second screening is called the 2nd trimester screening. It takes place between 16 and 20 weeks. The most informative period is considered to be 16-18 weeks.
The study includes ultrasound diagnostics of the fetus, as well as biochemical blood tests - a double, triple or quadruple test. When conducting a study, it no longer plays a big role in whether a woman will undergo both examinations at the same time.
Not so long ago, it was believed that if the first screening did not show abnormalities, then the second was not necessary at all, with the exception of women at risk.
Now second trimester screening is also considered mandatory, like the first, however, its data do not already represent such an important diagnostic value as the indicators of the first study in the first trimester.
So, in the office of ultrasound diagnostics, a pregnant woman is waiting for a usual and already familiar procedure, which will be carried out either transvaginally (if the woman is full and the view through the abdominal wall is difficult), or transabdominal (with a sensor on the abdomen).
The diagnostician will carefully study the baby, assess his physical activity, the presence and development of all organs.
There are no specific markers, such as the thickness of the collar space, with ultrasound in the first trimester, in the second study.
The general development of the child is assessed, and the data obtained are correlated with the variants of the average standard values for a given age of gestation.
Fetometric standards for ultrasound at screening of the 2nd trimester:
Deviations from the averaged parameters can speak not only of some pathologies, but also of hereditary features of appearance. Therefore, an experienced diagnostician will never scare a pregnant woman with the fact that her child has too big a head, if he sees that mom's head is also rather big, and dad (who, by the way, you can take with you to the ultrasound office) is also not of the type people with a small skull.
Children grow up in leaps and bounds, and a slight lag behind the norm does not mean that such a baby is not getting enough nutrition, suffers from malnutrition or congenital diseases. The deviation from the standard values indicated in the table will be assessed by the doctor individually. If necessary, the woman will be prescribed additional diagnostic procedures.
In addition to the fetometric parameters of the baby, in the ultrasound diagnostics room at the screening of the middle of pregnancy, the woman will be told about how the toddler is located in space - upward or upside down, his internal organs will be examined, which it is very important to understand if there are any defects in their development:
- lateral ventricles of the brain - normally do not exceed 10-11.5 mm;
- the lungs, as well as the spine, kidneys, stomach, bladder are indicated as "normal" or "N" if there is nothing unusual about them;
- the heart must have 4 chambers.
The diagnostician pays attention to the location of the placenta. If in the first trimester it was located low, then the chances that the child's place will rise by the second screening is great. It is taken into account on which wall of the uterus it is fixed - on the front or back.
This is important for the doctor to be able to decide on which method to give birth.
Sometimes the location of the placenta on the anterior uterine wall increases the likelihood of detachment; in this state of affairs, a cesarean section may be recommended. The maturity of the placenta itself at the time in which the second study is carried out has a zero degree, and the structure of the child's place should be homogeneous.
Such a concept, kato IAZH - index of amniotic fluid, indicates the amount of water. We already know that some congenital malformations are accompanied by oligohydramnios, but this index in itself cannot be a symptom of genetic diseases. Rather, it is needed to determine the tactics of further pregnancy management.
Amniotic fluid index rates:
Particular attention in the study as part of the second screening is paid to the condition and characteristics of the umbilical cord - the cord connecting the child with the placenta. Normally, it contains 3 vessels - two arteries and one vein. They are used to exchange between the child and the mother. The baby receives useful substances and blood saturated with oxygen, and metabolic products and blood containing carbon dioxide go back to the mother.
If there are only 2 vessels in the umbilical cord, this may indirectly indicate Down's syndrome and some other chromosomal abnormalities, but it is also possible that the work of the missing vessel is compensated by the existing one, and the child is healthy. Such babies are born weaker, underweight, but they do not have genetic abnormalities.
The doctor will advise the pregnant woman not to worry about the missing vessels in the umbilical cord if other ultrasound readings are within normal limits, and a double or triple test (biochemical blood test) does not show pronounced abnormalities.
The blood test is most often a triple test. In a sample of venous blood of the expectant mother, the concentration of free hCG, free estriol and AFP (alpha-fetoprotein) is determined. These substances give an idea about the course of bearing a child and about the possible risks of genetic pathologies in the baby.
The standards for different laboratories are individual, the values in MoM are used to summarize the various data. Each of the three markers is ideally somewhere between 0.5-2.0 MoM.
HCG level at the second screening:
An increase in the level of this hormone in the second screening more often indicates that a woman has gestosis, she has edema, protein in the urine, she took or is taking some hormonal drugs, for example, to maintain pregnancy.
The level of hCG is increased in women carrying twins or triplets. Sometimes an increase in the value of this substance indicates that the date has been set incorrectly, an adjustment is required.
Chromosomal abnormalities such as Down's syndrome can be signaled by a significant excess of the upper threshold of hCG, while a significant decrease in the other two components of the triple test. Alpha-fetoprotein and estriol hormone are pathologically underestimated.
Free estriol level in the second screening:
A slight excess in the concentration of this female sex hormone may be due to multiple pregnancies or the fact that a woman is carrying a large fetus.
A decrease in this hormone may indicate the likelihood of neural tube defects, and Down's syndrome or Turner's disease, as well as Patau's syndrome or Cornelia de Lange. Not every decrease in this substance is considered pathological; doctors begin to sound the alarm when the level is reduced by more than 40% of the average value.
A reduced level of estriol can sometimes indicate a flared up Rh-conflict, the threat of premature birth, as well as insufficient placental nutrition of the child.
AFP level in the second trimester
A significant excess of the alpha-fetoprotein index may be an indirect sign of the child's absence of a brain in whole or in part, pathological softness of the spine and other conditions inherent in congenital malformations of the neural tube.
For pregnant women expecting twins or triplets, an increase in ACE is the absolute norm.
A decrease in the level of this substance in the blood of the expectant mother may be an indication of a completely normal pregnancy, at the same time, in combination with an increased hCG and a low estriol, this indicator sometimes indicates a possible Down syndrome.
If the fetus is perfectly healthy, a decrease in AFP sometimes accompanies maternal obesity or a woman's history of diabetes mellitus. The low location of the placenta also affects the level of this substance, AFP may be below normal.
The results and results of the second trimester screening are also calculated using a special computer program, but taking into account the data and the first screening study.
Only a doctor can help a woman decipher the probability of having a sick baby.
An experienced obstetrician-gynecologist always personally "checks" the prediction of the computercomparing the concentrations of individual substances with the history of the pregnant woman, her anamnesis, personal characteristics, as well as with the protocols of the first and second ultrasound examination.
Third screening and its results
The final, third screening of hereditary diseases and other fetal pathologies is carried out at 30-36 weeks. Most often, doctors try to schedule a study for 32-34 weeks. The examination includes an ultrasound examination, as well as a kind of result of two previous studies.
As part of the screening, CTG (cardiotocography), this method allows you to establish how the heart rate of the toddler changes during his movements, how many of these movements are large.
For women at risk, not only a control ultrasound is performed, but also an ultrasound scan (ultrasound dopplerography) is prescribed, which allows to assess the blood flow rate in the uterine arteries. This allows you to get a more accurate idea of how the unborn baby feels, whether he has a state of hypoxia, whether he has enough nutrients.
On ultrasound, the diagnostician reports the fetometric data of the child, his position in the uterus, the amount of water, and also assesses the thickness and degree of maturity of the placenta.
From 30 weeks usually the placenta "grows old" to 1 degree, and from 35 weeks - to the second. According to the thickness of the child's seat, experts judge the ability of this temporary organ to meet the needs of the crumbs for nutrients.
Placenta thickness when performed in the third trimester
The placenta can become thinner than provided by the norms in lean and slender women, as well as in expectant mothers who have had infectious ailments during gestation.
Thickening of the child's seat often indicates the presence of a Rh-conflict, it is characteristic in the third trimester of women suffering from diabetes mellitus, gestosis. The thickness of the placenta is not a marker of chromosomal pathologies.
Fetometry of babies at these times may already differ significantly from the standard values, because everyone is born with different parameters, weight, each is similar to his mother and father.
Blood tests for biochemical markers are not taken in the third trimester. They are limited to the usual list of tests - general blood and urine tests.
If the screening showed abnormalities
If the verdict of a computer program that analyzes the data obtained as a result of screening shows a high risk of having a child with developmental pathologies, chromosomal and hereditary diseases, this is unpleasant, but not fatal.
All is not lost, and the child may well be healthy. To clarify this issue in detail, a woman may be assigned invasive studies.
The accuracy of such methods is close to 99.9%. The expectant mother is told about them in detail and is sure to give time to think about whether she really wants to know the truth at any cost, since one way or another, the procedures themselves, which make it possible to establish an accurate diagnosis, pose a danger to maintaining pregnancy.
To begin with, a woman is referred for a consultation with a geneticist. This specialist "double-checks" the results produced by the computer, and also directs them to invasive diagnostics.
For research, in this case, not samples of the mother's blood and tissues are taken, but tissue samples and blood of the baby himself, as well as amniotic fluid.
Any, even the safest method of the existing - amniocentesis - is associated with the risk of losing pregnancy. On average, the risks of infection and termination of pregnancy range from 1.5 to 5%. This cannot be ignored when agreeing to such a procedure.
If the results of the first screening are negative, the woman may be prescribed:
- Chorionic villus biopsy (up to 12 weeks)
- amniocentesis (amniotic fluid intake for analysis).
If the expectant mother and her attending doctor were alarmed by the results of the second screening, a decision can be made to carry out the following diagnostic procedures:
- amniocentesis;
- amnioscopy (visual examination of the ovum using a thin flexible endoscope - carried out only from 17 weeks of pregnancy);
- placentocentesis (collection for the analysis of the cells of the "child's place", carried out from 18 to 22 weeks);
- cordocentesis (blood sampling from a child for laboratory tests, carried out from 18 weeks);
- fetoscopy (examination of the child with an endoscope and taking a piece of fetal skin for analysis. The procedure can be carried out from 18 to 24 weeks).
A thin surgical instrument can be inserted in three ways - through the abdominal wall, through the cervical canal and through a puncture in the vaginal fornix. The choice of a specific method is the task of specialists who know exactly how and where exactly the placenta is located in a particular woman.
The whole procedure is carried out under the supervision of an experienced qualified ultrasound doctor, everything that happens in real time helps to track the ultrasound scanner.
The danger of such research lies in the possibility of early outpouring of water, termination of pregnancy. A crumb in the womb can be wounded with a sharp thin instrument, placental abruption, inflammation of the membranes can begin. Mom can get hurt, and the integrity of her intestines and bladder is at risk.
Knowing this, every woman has the right to decide for herself whether to agree to invasive diagnostics or not. Nobody can make her go to the procedure.
Since 2012, a new way of research has been carried out in Russia - non-invasive prenatal DNA test. Unlike the invasive methods described above, it can be done already at the 9th week of pregnancy.
The essence of the method is to isolate the child's DNA molecules from the mother's blood, since from the 8th week of pregnancy, the baby's own blood supply works, and part of his red blood cells enters the mother's bloodstream.
The task of the laboratory assistant is to find these red blood cells, isolate DNA from them and establish whether the child has congenital pathologies. At the same time, the technique allows us to find out not only the presence of gross chromosomal abnormalities, but also other gene mutations, which cannot be found out by any other means. Also, the mother will be informed with an accuracy of 99.9% of the baby's gender as early as 9 weeks of pregnancy.
Such tests, unfortunately, are not yet included in the health insurance package, and therefore are paid. Their average cost is from 40 to 55 thousand rubles. It is offered by many private medical genetic clinics.
The downside is that an invasive test with a puncture of the fetal bladder will still have to be passed if a non-invasive DNA test shows that there are abnormalities.
The results of such an innovative test are not yet accepted by gynecological hospitals and maternity hospitals as a basis for a long-term termination of pregnancy for medical reasons.
Preparing for screenings
The result of screening in an antenatal clinic can be false in both a positive and a negative direction, if a woman does not take into account the negative impact on her body of certain factors, such as medication or severe stress. Therefore, doctors recommend carefully preparing for a simple examination.
Three days before screening it is not recommended to eat fatty, fried and spicy foods. This can distort the results of a biochemical blood test.
The diet also includes avoiding chocolate, cakes, oranges, lemons and other citrus fruits, as well as smoked meats.
Donate blood on an empty stomach. But you can take crackers or a small chocolate bar with you to the consultation, so that after donating blood, you can eat it before undergoing the ultrasound procedure.
The child, under the influence of the chocolate eaten by his mother, will move more actively, and will be able to "appear" to the diagnostician in all its glory. An empty stomach does not mean that a woman should starve herself and her baby for three days. To successfully donate blood for biochemistry, it is enough not to eat for at least 6 hours before taking blood.
For a week, all stress factors should be excluded, from the evening before the examination, a woman should take a drug that reduces the formation of gas in the intestine, so that the "swollen" intestine does not cause compression of the abdominal organs and does not affect the results of ultrasound. A drug safe for expectant mothers - "Espumisan".
It is not necessary to fill the bladder, for this period (10-13 weeks) the fetus is clearly visible even without filling the bladder.
Research accuracy
The accuracy of second trimester screening is lower than that of the first screening, although its results raise many questions. So, sometimes it turns out that a woman who was put at high risks gives birth to a completely healthy baby, and a girl who was told that everything is “normal” becomes the mother of a baby with severe genetic pathologies and developmental anomalies.
Accurate research is considered only invasive diagnostic methods. The accuracy of screening detections of Down syndrome using blood tests and ultrasound is estimated by specialists at about 85%. Screening detects trisomy 18 with an accuracy of 77%. However, these are the figures of official statistics, in practice everything is much more interesting.
The number of false positive and false negative screenings has been on the rise lately. This is not due to the fact that doctors began to work worse. It's just that many women, hoping for the competence of paid specialists, try to undergo research for their own money in a paid center, and there ultrasound is not always carried out by specialists who have international admission to conduct just this type of research.
The number of incorrect analyzes is also growing, because even with modern equipment, living people work in laboratories.
There is always a chance that the doctor did not notice something during the ultrasound or that he saw something completely different from what it is, and that the laboratory technicians made an elementary technical mistake. Therefore, sometimes data from one laboratory should be double-checked in another.
It is best to undergo a screening study in a consultation at the place of residence - there doctors are guaranteed to have not only admissions to this kind of diagnosis, but also extensive experience in its implementation.
It is important to remain calm and believe that everything will be fine with the child, without giving up the opportunity to learn as much as possible about the baby's condition. Screening provides just such an opportunity.
