Perinatal screening for the 2nd trimester of pregnancy. What to do if a woman has poor screening test results. Explanation of the results of the "triple screening test"

13.06.2019

Pregnancy is a crucial period in a woman's life, proceeding according to special rules. They determine not only the nature of nutrition, daily routine, exercise regimen, but also require regular monitoring of the condition of both the expectant mother and the baby in her womb. After the first large-scale examination, performed at 11-13 weeks, it is time to undergo a 2nd trimester screening, which includes a second ultrasound scan and a biochemical blood test. Its purpose is to confirm or deny the development of pathologies, to detect their direct and indirect markers. So, to whom is such a diagnosis indicated? What does it include, and how are the indicators deciphered? How to properly prepare for the procedures, and how do they occur?

In order to obtain the most accurate information, the second screening is carried out within the time frames clearly stipulated by the standards:

biochemical blood test - from the 15th to the 20th week, while the interval from the 16th to the 18th week is considered the optimal period. It was at this time that the information content of the study for determining the biochemical formula and composition of hormones is maximum;
2nd trimester perinatal ultrasound screening: ideal is 19-24 weeks. It is performed after passing biochemistry. As a rule, ultrasound is prescribed in the period from 19 to 22 weeks, and if complications are suspected, a second scan may be indicated from 22 to 24 weeks. For special indications, the scheduled screening period may be shifted to an earlier date and carried out starting from the 16th week.

It is not necessary to pass the listed studies at the same time. You can distribute them over time so as not to be overwhelmed. It should be remembered that if an ultrasound scan can be transferred or performed again at any time, then there is a strict framework for taking a blood test due to the variability of its composition over the course of pregnancy.

Who is the second screening shown to, and can we refuse it?

2 screening is a set of examinations that the Ministry of Health strongly recommends to undergo every pregnant woman at the appropriate weeks. It is mandatory for representatives of the risk group, that is, if at least one of the conditions is met:

the parents of the unborn child are close relatives;
an infectious disease transferred in the early stages, especially in the period of 14-20 weeks;
a history of genetic disease of one of the parents, older children;
previous pregnancies ended in miscarriages;
children born earlier with developmental delay or pathologies of the nervous system;
serious deviations from the norm identified during the first screening, the threat of disruption of gestation;
the age of the future woman in labor is over 35;
oncopathology revealed after the 14th gestational week;
radiation exposure to which the father or mother of the child was exposed on the eve of conception or immediately after it.

If an oncological disease is detected, the patient is referred for a consultation with a geneticist, who usually prescribes additional examinations: a repeated ultrasound scan or an additional biochemical blood test. This is done to assess the danger of the patient's condition and to decide whether to prolong or terminate the pregnancy.

The second screening is not compulsory. If the expectant mother fears that the examination may harm the child's health and her own, she has the right to write a written refusal to carry out the diagnosis. The doctor is obliged to provide the application form upon request. At the same time, he must explain to the patient all the risks to which she exposes both herself and the baby.

What they look at at the second screening during pregnancy

The tasks of the second screening include the study of not only fetometric parameters, but also the functional characteristics of the vital organs of the fetus, namely:

spine, skull and other bones of the skeleton;
facial features (eyes, nose, mouth);
kidneys, bladder and other elements of the genitourinary system;
the myocardium and the entire circulatory system;
digestive organs, including the stomach and intestines;
brain, spinal cord and related structures;
components for calculating BPD (biparietal size), LZR (frontal-occipital size), coolant (abdominal circumference), OG (chest circumference), length of paired bones.

With a good location, the diagnostician is able to determine the sex of the unborn child by the gender characteristics that were formed at the time of the study.

In addition to analyzing the development of the baby's organs and systems, the state of the mother's body is assessed, since the viability of the fetus depends on it. The examination program includes scanning:

placenta, its location, thickness, size, structure, maturity;
amniotic waters, their quantitative characteristics;
the umbilical cord, the presence of all the main vessels;
uterus, its cervix and appendages.

During the procedure, the position of the fetus in the placenta is assessed.

Based on the results obtained, the doctor draws conclusions about the presence or absence of pathologies of the course of pregnancy, the sufficiency of blood and oxygen supply, the correct development of the fetus, as well as the presence or absence of a threat to the health and life of the child and mother.

Preparation for the survey

The screening schedule consists of two main procedures: a 2nd trimester ultrasound scan and a biochemical blood test.

If an ultrasound scan is performed abdominal, then a maximally filled bladder is required to visualize the area under study. This can be achieved by drinking at least one liter of water. If an intravaginal examination is planned, then, on the contrary, it is recommended to refrain from excessive fluid intake.

Before donating blood, you need to prepare more thoroughly. In order to ensure the maximum informational value of the results, one day before taking the biological material, one should refuse fatty, spicy and fried foods, fish and other seafood, chocolate and cocoa, citrus fruits. It is forbidden to eat 5-6 hours before the visit to the laboratory. In case of severe thirst, it is allowed to drink no more than one glass of water without gas, but no later than 30-40 minutes before manipulation. If possible, the patient should avoid stressful situations.

How is the procedure performed

The second screening begins with an ultrasound scan.

Routine prenatal ultrasound screening is no different from the standard one. During the procedure, the woman sits comfortably on the couch, the diagnostician lubricates the skin in the places of her contact with the sensor with hypoallergenic gel. Information is read through the anterior abdominal wall in the abdominal form of the study, through the vagina in the transvaginal form. After a few minutes, the transcript of the results is given to the patient in her arms.

Before performing a biochemical blood test, the observed must provide an ultrasound transcript and a special questionnaire. Based on this information and a preliminary conversation with the pregnant woman, the doctor decides on the need to determine the concentration of a number of additional elements in the blood. The sampling of material for research is done from a vein. Its analysis is performed using a special computer program. The survey results are ready within two weeks.

What is included in the list of examinations

The second perinatal screening involves two mandatory procedures:

ultrasound examination;
biochemical blood test.

In some cases, for example, if a future woman in labor had to perform an unscheduled blood test at an earlier date, she will only be assigned a second ultrasound.

A complete biochemical test as part of this routine study involves determining the concentration of four elements in the blood:

HCG (human chorionic gonadotropin) - a hormone produced by chorionic tissues after embryo implantation;
AFP (alpha-fetoprotein) - a protein that is produced by the liver and gastrointestinal tract from the 3rd week of the existence of the embryo;
EZ (free estriol) - a hormone that is synthesized by the liver and adrenal glands of the fetus;
inhibin A - a specific female hormone, the concentration of which varies depending on the timing of pregnancy and the condition of the fetus.

This analysis is called a quadruple test. In comparison with the screening program for the first trimester, the measurement of the content of the last two indicators - free estriol and inhibin A is added to the tasks of the quadruple test.

If there are no indications for studying the concentration of inhibin A in a pregnant woman, then only hCG, AFP and EZ are analyzed. Such a study, respectively, is called a triple test.

Factors influencing results

In the course of any examination, both false positive and false negative results can be obtained. Factors that can distort the results of screening (especially for a blood test for hormones) are:

chronic diseases of the expectant mother, including diabetes mellitus;
bad habits (consumption of alcoholic beverages and drugs, smoking);
overweight or underweight pregnant woman. In the first case, the indicators are overestimated, in the second, they are underestimated;
the patient's age is over 35 years old;
pregnancy with twins, triplets and so on;
IVF conception;
taking certain hormonal drugs.

If dangerous pathologies are identified, in order to confirm or refute the diagnosis, the woman will be assigned additional non-invasive (repeated ultrasound) or invasive (cordocentesis, amniocentesis) examinations. Depending on the results obtained, the doctor will recommend that the pregnancy be abandoned or terminated. The final decision is made by the patient herself.

Interpretation of test results and ultrasound and standard indicators of the second trimester

After the patient has passed all the mandatory procedures included in the second screening, the supervising obstetrician-gynecologist proceeds to decipher the results. It is based on data from tables that show the rates of all indicators in accordance with the duration of pregnancy. The doctor must compare the values of hormones and protein in the patient's blood with normal values, on the basis of which to draw conclusions about the health of the mother and fetus. Based on the results of an ultrasound scan, they are assessed and compared with age standards:

the size of the fetus;
facial features (condition of the eyeballs, nasal bone, absence of pathologies);
internal organs (heart, lungs, kidneys, liver, gastrointestinal tract, and so on);
amniotic water (their amount and content);
the placenta (its thickness and structure).

Blood

The norms of blood biochemistry indices in the framework of the 2nd screening depend on the duration of pregnancy. Their values are shown in the table.

When performing the fourth test, the blood level of the FSH secretion inhibitor is assessed. The concentration of the hormone in a singleton pregnancy should not exceed 500 pg / ml, in a multiple pregnancy - 600 pg / ml.

MoM

A generalized assessment of biochemical screening is made based on the average values of the indicators. It is expressed in the value of MoM - a coefficient showing the degree of deviation of the obtained results from the norm. It is calculated as the ratio of the obtained value of the indicator in the blood serum to the median, characteristic for a given period of pregnancy. The MoM formula also contains variables such as:

body weight of the patient;
her age;
territory of residence.

Values in the range of 0.5-2.5 MoM are considered normal. If this requirement is not met, the woman needs to consult a geneticist, since such a discrepancy indicates an increased risk of having a child with Down, Patau, Edwards and several others.

A risk ratio not exceeding 1: 380 is considered acceptable. If the predicted figure falls within the range of 1: 250… 1: 360, it is necessary to listen to the opinion of a specialist in genetic disorders. If the risk is high (above 1: 100), additional research, including invasive ones, is strongly recommended. The likelihood of having a child with deviations in this case is very high.

Body length and fetal weight

The beginning of the second trimester is marked by the intensive development of the fetus, therefore, it is difficult to say the standards for height and weight at this time. As a rule, the length of a child's body fluctuates between 10 and 16 cm. In this case, doctors pay attention not to absolute indicators, but to an increase per week.

The second planned ultrasound scan during pregnancy does not make it possible to directly determine the weight of the fetus in the womb. It is calculated by the formulas, and the result obtained has a serious error. On average, by the 20th week, the body weight is 300 grams, and by the 22nd week it can reach 450 grams.

Circumference of the abdomen and head

To say that pregnancy is developing correctly, the coolant (abdominal circumference) must correspond to the following values, depending on the period:

16 weeks - 88-116 mm;
17 weeks - 93-131 mm;
18 weeks - 104-144 mm;
19 weeks - 114-154 mm;
20 weeks - 124-164 mm;
21 weeks - 136-176 mm;
22 weeks - 148-190 mm.

OG (head circumference) with normal development should be equal to:

16 weeks - 112-136 mm;
17 weeks - 121-149 mm;
18 weeks - 131-161 mm;
19 weeks - 142-174 mm;
20 weeks - 154-186 mm;
21 weeks - 166-198 mm;
22 weeks - 178-212 mm.

Biparietal (BPR) and fronto-occipital (LZR) sizes of the fetal head

BPD and LZR are two key indicators that indicate the absence of abnormalities in the baby. Depending on the term, the BPR should vary within:

16 weeks - 31-37 mm;
17 weeks - 34-42 mm;
18 weeks - 37-47 mm;
19 weeks - 41-50 mm;
20 weeks - 43-53 mm;
21 weeks - 45-56 mm;
22 weeks - 48-60 mm.

The following framework is established for LZR:

16 weeks - 41-49 mm;
17 weeks - 46-54 mm;
18 weeks - 49-59 mm;
19 weeks - 53-63 mm;
20 weeks - 56-68 mm;
21 weeks - 59-71 mm;
22 weeks - 63-75 mm.

Bone length: lower leg, femur, humerus and forearm

The correct formation of the child's skeleton is evidenced by the compliance with the accepted norms of DG (length of the leg bones), DB (length of the femur), DP (length of the humerus), DPP (length of the forearm bones). The established mean values corresponding to the gestational age are shown in the table.

Fetometric parameters

During an ultrasound scan, which is performed in the second trimester of pregnancy, such key fetometric parameters as OB, OH, BPD, LHR and the length of long bones are studied and analyzed. If the examination reveals a deviation from the median value, this is not an unconditional marker of pathology or deviation. The reasons may be different: there is a possibility of an error in determining the date of conception, or the parents have a slender physique, therefore, growth retardation may be caused by heredity. All fetometric characteristics must be analyzed in combination. It is not the absolute values of the indicators that are important, but the proportional relationship between them.

Brain and spine

Usually, to study the structures of the brain using ultrasound, two axial sections are used: transventricular and transcerebellar. The chresthalamic section is less commonly chosen. During the examination, the diagnostician looks at the cerebellum, lateral ventricles, cisterna magna and the cavity of the transparent septum. Head shape and brain texture are also evaluated. In a healthy child, all investigated elements should correspond to normal X-ray anatomy.

The main section for studying the state of the spine is longitudinal. It is very important that the three centers of ossification of the vertebrae are visible. The doctor examines the bones for the absence of open spinal hernia, sacral agenesis, and other abnormalities. As a rule, such pathologies are combined with disorders identified in the brain. With ultrasound, attention should be paid to the skin over the ridge. If necessary, the inspection continues with the selection of the cross-section.

Respiratory system

At the time the woman undergoes the examination, the respiratory system of the fetus is already fully formed. The examination focuses on the condition of the lungs and their degree of maturity. So, normally, each lung should occupy about a third of the cross-section of the chest.

The level of formation of this organ is assessed in the ratio of its echogenicity in comparison with the liver. There are three degrees of maturity:

0 - the echogenicity of the lungs is lower than that of the liver;
1 - the echogenicity of the compared organs is approximately equal;
2 - the echogenicity of the lungs is higher than that of the liver.

Heart

During an ultrasound scan, the doctor examines the condition and functionality of the heart. At the same time, the following indicators are assessed:

the location of the organ. Normally, at this time, it occupies a third of the chest;
position of the axis of the heart;
the size and condition of the heart chambers;
the shape of the interventricular septum;
tissue structure - myocardium, pericardium, enrocardia.

Pay attention to the heart rate and rhythm. The first parameter should normally be 140-160 beats per minute.

Digestive system

By the time of the second planned ultrasound, the fetus has already fully formed and is functioning the digestive system: the esophagus, stomach, pancreas, intestines. It is important to carefully examine the entire gastrointestinal tract: find the connection between the stomach and the esophagus, make sure that all organs are present, that there are no hyperechoic elements in them.

urinary system

The formation of the kidneys in the fetus begins already on the 22nd day from the moment of conception, and by the end of the second trimester this process is completely completed. Ultrasound allows you to accurately identify pathologies of the urinary system. Normally, the size of the kidneys is:

18 weeks - 16-28 mm;
19 weeks - 17-31 mm;
20 weeks - 18-34 mm;
21 weeks - 21-32 mm;
22 weeks - 23-34 mm.

The ratio of the size of the renal pelvis to the size of the entire renal pelvis system should not differ by more than 5 mm.

In most pregnant women, the adrenal glands of the fetus begin to be visualized on an ultrasound scan somewhere from the 20th week. Their size is about 9-10 mm. The correct ratio of the size of the kidneys and adrenal glands is considered to be 0.48-0.65. In this case, the left adrenal gland should be larger than the right one.

Signs of pathology

The second screening is designed to identify and prevent the development of deviations and diseases.

Signs found on ultrasound scans are important markers for genetic abnormalities and other abnormalities:

lag in fetal development;
prolapse of the placenta;
polyhydramnios or low water, the content of flakes and suspensions in amniotic waters;
thickening of the walls of the placenta, its early aging;
disproportionate ratio of fetometric characteristics;
irregular shape of the facial bones, especially the nasal;
ventriculomegaly, or an increase in the lateral ventricles of the brain;
cerebral vascular cyst;
pyelectasis, or enlargement of the renal pelvis, and others.

Abnormalities are also indicated by deviations in the biochemical test results.

An increase in hCG levels may indicate the risk of developing Down's or Klinefelter's syndromes, and a decrease in the level of Edwards syndrome.

Defects of the nervous system, liver necrosis, absence of the esophagus, umbilical hernia and Meckel's syndrome are indicated by the deviation of the AFP value from the average to a large side. The opposite violation is a symptom of Down and Edwards syndromes, and may also indicate the death of the fetus or an incorrectly determined date of conception.

An elevated E3 level can indicate both liver and kidney problems in the mother, as well as a large baby or multiple pregnancies. But the deficiency of this hormone is a symptom of infection, placental insufficiency, adrenal hypertrophy, trisomy, anencephaly and a marker of the risk of premature termination of gestation.

Excessive content of inhibin A in the blood may indicate placental insufficiency, oncological process, genetic abnormalities, and insufficient - about the threat of self-abortion.

Possible diseases

Some pathologies are preliminary detected even at the first prenatal screening and according to the results of a blood test. The second routine screening ultrasound is intended to confirm or refute such suspicions. It is used to diagnose trisomies (Down, Edwards, Patau, de Lange syndromes) arising from an extra chromosome in one of the rows, anomalies of the central nervous system, facial structures, and so on.

Down Syndrome

Down syndrome is one of the most common chromosomal abnormalities in the fetus. It develops due to the appearance of an extra chromosome in the 21st chromosome row. Children born with such a pathology have a specific appearance, suffer from various diseases of internal organs, and lag behind in development. Very often, such people live for a relatively short time.

Down syndrome can be suspected already at the stage of blood biochemistry. It is evidenced by an increased level of hCG and a decreased level of AFP and estriol.

On ultrasound, the described pathology is characterized by a thickening of the collar zone and a shortened nasal bone.

Neural tube defect

There are several types of neural tube defects:

spina bifida, when the spinal cord protrudes at its base;
anencephaly - unformed in the upper part of the brain and skull, the absence of hemispheres;
encephalocele, in which the brain and membranes protrude through the cranial vault;
Chiari malformation - the penetration of brain tissue into the spinal column.

Such pathologies are perfectly visualized by ultrasound and are manifested by an increase in the AFP level (less often - by a drop in free estriol).

Edwards syndrome

The cause of the manifestation of Edwards syndrome is a genetic mutation associated with duplication of the chromosome in the 18th pair. The disease is manifested by the features of appearance and its inherent disorders of the work of internal organs, motor skills and psyche. Unfortunately, the mortality rate in the first year of life in children born with such a defect reaches 90%.

On ultrasound screening, pathology is manifested by characteristic anomalies in the structure of the skull and face, abnormalities in the structure of the skeleton, urinary and cardiovascular systems. The blood test results show decreased protein, hCG and estriol.

False results

The second screening is characterized by a high degree of objectivity. According to various sources, its diagnostic reliability is estimated at 60-90%. The probability of receiving false positives does not exceed 2.5%.

Distorted data are obtained if the patient is obese (the level of hormones in the blood increases), diabetes mellitus (hCG decreases), is pregnant with twins, and also if IVF has taken place (the protein level is 10-15% lower, hCG is overestimated).

A normal outcome does not guarantee a healthy baby, as some physical defects or mental retardation may be caused by unknown factors.

How often can an ultrasound scan be done in the second trimester?

The regulatory documents of the Ministry of Health of Russia establish the obligatory conduct of three ultrasound examinations during pregnancy (one in each trimester at a clearly specified time). In case of problem bearing, the number of such procedures may be more than ten.

Ultrasound is recognized as a safe form of diagnosis for pregnant women. The doses and intensity of ultrasound used are not capable of causing harm to the human fetus. Even the WHO officially allowed four sessions during pregnancy, but, if possible, not earlier than the 10th week.

Further actions

If, according to the results of the second prenatal screening, the doctor has concluded that the pregnancy is normal, the expectant mother is in excellent condition and the healthy child, the next group of examinations is to be carried out in the period from 30 to 32 weeks as part of the third scheduled screening.

If pathologies are identified or the risk of their development is increased, the patient may be referred for repeated ultrasound or invasive diagnostic procedures: chorionobiopsy, cordocentesis, amniocentesis. In some cases, it is necessary to observe a geneticist up to delivery.

If a condition is diagnosed that means the child is not viable, his deformity, lag in physical and mental development, termination of pregnancy may be recommended. The final decision is made by the patient herself.

With the onset of pregnancy, every woman periodically visits a doctor, takes laboratory tests, undergoes an ultrasound examination (screening of the 2nd trimester), which allows us to assess the condition of the fetus, to identify the slightest changes or developmental pathologies. Throughout pregnancy, a woman must undergo three routine examinations. If a pathology is suspected, a woman has a history of chronic diseases, the number of ultrasound procedures can be increased. It has been proven that ultrasound is a safe and informative research method that does not harm the fetus and does not affect the course of pregnancy. The doctor must prescribe screening, which is a complex of studies, including ultrasound diagnostics and laboratory tests of blood and urine. The diagnostic results help the doctor determine the norms and possible complications, recognize anomalies or congenital pathologies.

The second screening of pregnant women is carried out in the second trimester of the gestational period. It is mandatory and takes place at 16-19 weeks. The main indicators that the doctor pays attention to are (human chorionic gonadotropin), AFP (alpha-fetoprotein) and free estriol (E3), as well as ultrasound results. If a pathology is suspected, a screening test may be prescribed to assess the hormonal background. Screening for the 2nd trimester should not intimidate a pregnant woman, as it is a mandatory test method. If the pregnancy proceeds without complications, it is not necessary to undergo a full diagnosis, you can do with ultrasound diagnostics. In order to get acquainted with the screening in more detail, it is important to know when it is prescribed, what its norms and deviations are, as well as how to properly prepare for the procedure in order to obtain the highest possible results.

Do pregnant women need to undergo a second screening

The main purpose of screening in the second trimester is to identify defects in the development of the fetus and to establish possible risks for the expectant mother. This research method is prescribed to confirm or deny various risks that were obtained during the initial diagnosis in the first trimester. Full screening is not prescribed for all women, but only for those who are at risk, suffer from chronic pathologies or have a hard time bearing a child. The following conditions and diseases are considered the main indications for diagnostics:

woman's age after 35 years;
poor heredity;
genetic diseases;
viral diseases in the first trimester;
miscarriages, fetal freezing, in the past;
conceiving a child by close relatives;
parental dependence on drugs, alcohol;
taking medications that are prohibited during pregnancy;
autoimmune diseases;
chronic diseases of internal organs and systems that can harm the fetus, affect its growth and development.

Other diseases or conditions that can lead to the development of fetal pathologies may also be indications for screening. To carry out a diagnosis, it is not necessary to have any health problems. If a woman wishes to undergo a screening to make sure that the fetus is developing healthy, the doctor will definitely give directions. The procedure is completely safe for both the woman herself and her unborn child.

What do they look at ultrasound in the second trimester

In, the fetus is fully formed, so doctors, having on hand the results of examinations, can easily determine whether there are deviations or pathologies in its development. The second screening examination allows the doctor to identify many fetal pathologies, including:

defects of the brain or spinal cord;
liver pathology;
abnormalities of the gastrointestinal tract.
facial cleft;
heart defects;
defects of the limbs, trunk.

Abnormalities and defects that can be detected at the 2nd screening are often not subject to correction, often serve as an indication for termination of pregnancy for medical reasons. In addition to pathologies, this research method determines the presence of markers of fetal chromosomal abnormalities, including:

delayed development of the embryo;
a lot or lack of water;
pyeloectasia;
ventriculomegaly;
underdeveloped length of the tubular bone;
cysts of the choroid plexuses of the brain or spinal cord.

Thanks to the results, it is possible to identify other pathologies in the development of the fetus. Ultrasound diagnostics also allows you to obtain informative results on the development and growth of the fetus, to assess the norms and deviations:

facial structure (size of the nasal bone, nose, ears, eyes);
size, weight of the fetus;
lung maturity;
the structure of the brain, heart, blood vessels, intestines and other internal organs;
the number of fingers on the upper and lower extremities;
the thickness and degree of maturity of the placenta;
condition of the uterus and its appendages;
the amount of amniotic water.

Ultrasound examination in the 2nd trimester makes it possible to determine the sex of the child with an accuracy of 90%, to reveal the slightest disturbances in his development. After the passed screening, all the results and transcripts are attached to the card of the pregnant woman, and given to the doctor who leads the pregnant woman.

Screening of the 2nd trimester includes blood sampling from a vein, which is considered mandatory if a pathology is suspected. If the ultrasound results are satisfactory and there is no suspicion of an abnormality, a blood test may not be ordered. Unlike the first trimester, a blood test in the 2nd trimester evaluates slightly different parameters, including:

the amount of human chorionic gonadotropin ();
free estriol;
alpha-fetoprotein (AFP) indicators;
the content of inhibin A.

Ultrasound and blood tests during the second screening with an accuracy of 85% determine the dynamics of genetic abnormalities that were identified in the first trimester.

After passing all the tests, the results will be ready within a week. Only a doctor can decipher their results. With good screening results, serum ACE levels should be approximately 15 to 95 U / ml. With poor results, the protein level will be increased, which may be a sign of pathologies such as esophageal atresia, liver necrosis, and others. With a reduced protein, the risk of fetal development or death increases.

Screening indicators of the 2nd trimester are very important for a pregnant woman and a fetus, therefore it is very important not only to properly prepare for the examinations, but also turn to a qualified doctor for decoding. It is important to understand that the life of the unborn child depends on the correct decoding.

How to prepare for a second perinatal diagnosis

For screening in the second trimester, special preparation is not required, but nevertheless, in order to obtain reliable results, a woman must follow some rules.

Blood must be taken on an empty stomach. Eating any food, as well as liquids, can distort the analysis results. It is best to take a blood test in the morning.
1 day before donating blood, you need to refuse sugary foods, as well as foods that may cause an allergic reaction.
Ultrasound does not require any preparation. It is not necessary to fill your bladder. Diagnostics can be performed at any time of the day.

Many doctors in the field of obstetrics and gynecology assure that a woman needs moral training, the support of relatives. It is important for a woman to tune in to positive results, to hope and believe in good results.

When is this study done?

Screening in the 2nd trimester of pregnancy is recommended not earlier than the 16th, but no later. Many doctors recommend diagnosing at 17-18 weeks. It is during this period that it is possible to assess the condition of the fetus with high accuracy, to identify the slightest changes and pathologies in the development of the fetus.

In the presence of fetal abnormalities or suspicion of them, other additional diagnostic methods may be prescribed in the second trimester. A pregnant woman can be assigned a consultation with a geneticist and other specialists.

How the research is done

Ultrasound and blood tests must be performed in the same clinic on the same day. These diagnostic methods do not cause any inconvenience to a woman, except for those who are afraid to donate blood from a vein.

Ultrasound is performed by the transabdominal method, that is, the doctor applies the gel to the woman's abdomen, using a sensor that touches the skin, the doctor receives a picture on a computer monitor, from which he reads and records information about the state of the fetus. The procedure takes 15 to 30 minutes.

After the results of an ultrasound scan, revealing any pathologies, the doctor sends the woman for a biochemical blood test. In the event that any pathologies are present, the woman in the laboratory donates blood from a vein. The sampling volume is from 3 to 5 ml.

The results of laboratory diagnostics need to wait for several days, while the transcript of an ultrasound scan can be obtained immediately after the procedure. After the obtained results of the study, the doctor compares them with the indicators of the norm and deviations. Against the background of the results of the examination, the specialist has the opportunity to get a complete picture, identify or exclude pathologies, and give useful recommendations. If necessary, other research methods may be prescribed to a pregnant woman.

Decoding of the obtained results

Screening of the 2nd trimester consists of indicators, each of which has its own norm. In some cases, the results may deviate from the norm, since it all depends on the duration of pregnancy, the course of the pregnancy itself, and the characteristics of the female body.

Depending on the clinic, laboratory, the results may vary slightly, so doctors recommend being examined only in clinics with a good reputation, where there is the latest equipment for laboratory and instrumental diagnostics.

The ultrasound is transcribed by an ultrasound doctor, and then transferred to the attending physician. Only a doctor can deal with analyzes, ultrasound results.

With increased or decreased rates, there is a risk of pathology in the fetus and woman.

A lowered AFP level is a sign, fetal death or incorrect determination of the gestational age.
Increased AFP - malformations of the central nervous system, Meckel's syndrome, liver pathology (necrosis).
High - or Klinefelter.
Low - high risk.
Reduced estriol - intrauterine infection, Down, placental insufficiency, risk of premature birth.
Elevated estriol - internal liver disease in the mother, multiple pregnancy, or a large fetus.

A blood test is not a definitive result for making a final diagnosis. If a pathology is suspected, amniocentesis is prescribed, which consists of piercing the abdominal wall followed by the collection of amniotic fluid. The results of this test give accurate results about the condition of the fetus with a probability of 99%.

Despite the alleged information about the indicators that may be present in the interpretation of the analysis and indicate the pathology of pregnancy, the doctor makes the final decision and only after repeated and additional tests.

Indicator standards

To decipher the results of the examination, the doctor compares them with the table of norms. If there are deviations, the specialist makes a conclusion, prescribes additional or repeated tests.

To decipher the screening of the 2nd trimester, the doctor can start from the table of the norm.

The table contains only the assumed decoding parameters, which indicate the normal course of pregnancy and the absence of any pathologies in the fetus.

Not only the decoding of the blood test is considered important, but also the ultrasound examination. Under normal conditions, the decryption will contain the following parameters:

Pregnancy 16 - 17 weeks.

Fruit weight - 100 - 140 g.
Fruit length - 11.6 - 13 cm.
Abdominal circumference - from 88 to 131 mm.
The head circumference is from 112 to 145 mm.
Frontal-occipital size (LZR) - from 41 to 49 mm.
Biparietal size - from 31 to 37 mm.
The length of the shin bone is from 15 to 25 mm.
The length of the femur is from 17 to 28 mm.
The length of the forearm bones is from 12 to 21 mm.
The length of the humerus is 15 to 25 mm.
The amniotic fluid index is 73-211.

Pregnancy 18 - 19 weeks

Fruit weight - 190 - 240 g.
Fruit length - 14.2 - 15.3 cm.
Abdominal circumference - from 104 to 154 mm.
The head circumference is from 141 to 174 mm.
Frontal-occipital size (LZR) - from 49 to 63 mm.
Biparietal size - from 37 to 49 mm.
The length of the shin bone is from 20 to 31 mm.
The length of the femur is from 23 to 34 mm.
The length of the forearm bones is from 17 to 26 mm.
The length of the humerus is 20 to 31 mm.
The amniotic fluid index is 80-225.

The research results allow the doctor to determine the important indicators in the development of the fetus are characteristic of. However, the final decision is made by the doctor individually for each patient.

Answers to the most common research questions

Women who are scheduled for screening in the 2nd trimester of pregnancy always experience anxiety, especially when it comes to possible pathologies. When consulting a doctor, women often ask doctors questions, which we will try to answer.

Q: What is the best week of pregnancy for the 2nd screening?

Answer: The examination of the 2nd screening can be carried out at a period of 16 -. The most accurate results can be obtained at 17-18 weeks.

Question: Is it obligatory to donate blood from a vein at the 2nd screening?

Answer: If a pathology is suspected, it is obligatory. When the ultrasound results show normal values, there are no deviations from the norm, the pregnancy is proceeding well, the analysis may not be carried out.

Question: What is included in the examination of the 2nd screening?

Answer: Screening of the second trimester consists of ultrasound diagnostics and analysis of venous blood.

Question: Is it mandatory to do a second screening?

Answer: If at the first screening in the 1st trimester pathologies were found, the pregnancy is difficult, the woman is over 35 years old or has a history of chronic diseases, then it is imperative.

Screening cost for the 2nd trimester

The cost of the 2nd screening directly depends on the clinic, possible additional research methods. The price for a full examination can range from 2500 to 4000 thousand. rubles. In some state clinics, it is possible to undergo the procedure for free, but given that medical centers, private clinics and laboratories have more modern and accurate equipment, if you suspect a pathology, it is better to turn to them.

Screening of the 2nd trimester is one of the important research methods that allow timely identification of abnormalities in the development of the fetus. In case of poor results, defects or defects in the development of the fetus, it is recommended to terminate the pregnancy for medical reasons.

The second trimester of pregnancy for many women is marked by screening, a triple test for fetal chromosomal abnormalities. This study is considered slightly less informative than the one that is conducted at the end of the first trimester. But nevertheless, biochemical screening of the 2nd trimester and ultrasound can and are considered as objective data for calculating risks and even making an accurate diagnosis.

What is this study, what is its information content, can there be errors? Screening of the 2nd trimester is a complex of medical measures, a blood test from a vein and an ultrasound scan, the results of which are entered into a computer program that calculates the risks of Down syndrome, Edwards, Patau, Turner, triplodia and others.

In this case, the decoding of the results of biochemical screening of the 2nd trimester is issued by the program in the form of a quantitative risk. For example “Down syndrome - 1: 1800. And this means that one woman out of 1800 of the same age, with the same features of the course of pregnancy, the results of ultrasound and blood tests, gives birth to a child with this pathology.

Since many women simply do not take risk numbers seriously, they decide to undergo only part of this examination. Namely, ultrasound screening of the 2nd trimester, which can clearly show malformations of organs and systems of the fetus, suggest that he has a genetic disease based on some markers, such as shortening of the nasal septum or the absence of the phalanx of the little finger. In addition, prenatal screening of the second trimester makes it possible to diagnose overt congenital malformations of the face, heart, stomach, brain and spinal cord, urinary system, and honesty of the kidneys. Many of these pathologies are indications for artificial termination of pregnancy, since they cannot be treated with surgery and make the fetus unviable. Some markers can also be identified that indicate genetic abnormalities, but not always. For example, renal pyelectasis, hyperechoic inclusions in the heart, hyperechoic intestines, etc. These markers require re-examination. And blood screening of the 2nd trimester is very useful in this case. But even if the screening results are good, the ultrasound is repeated after 2-3 weeks. It is highly desirable to do an ultrasound of an expert class, to consider problem areas, including in 3D mode, so the information obtained will be more accurate.

Screening of the 1st trimester and the second screening during pregnancy differ in the methods of carrying out. So, at the first screening, it is very important to accurately observe the timing of the blood test and ultrasound. This must be done on the same day. And the timing of the second screening during pregnancy for ultrasound and biochemical analysis is different. So, the expectant mother donates blood for alpha-fetoprotein (AFP), free β-hCG and extriol for a period of 16-18 weeks. It is imperative to comply with this deadline! But ultrasound is most informative for a period of 20 weeks. Moreover, only biochemical screening is effective no more than 70%. That is, about 30% of favorable blood test results turn out to be false-negative; those who took them will have children with Down's or Edwards syndrome.

At the same time, adverse 2-trimester screening results are usually indications for invasive diagnostics. For longer periods, this is either amniocentesis (at 16-20 weeks) or cordocentesis (more than 20 weeks). Moreover, amniocentesis is less dangerous in terms of complications in the form of spontaneous late miscarriage or premature birth. Sometimes it happens that the screening of the 2nd trimester of the norm by ultrasound shows, and a child with the syndrome is born ... The reason for this is the absence of any markers of chromosomal pathologies, poor visualization during ultrasound examination, and sometimes even the doctor's inattention.

Many women are poorly versed in how to do ultrasound screening for the 2nd trimester, blood tests are taken. And they are trying to pass these examinations on their own. They make mistakes in the timing, get the results of blood tests without calculated risks - all this makes the screening completely unreliable. After all, decoding the results of second trimester screening is the task of a special computer program, and not of a pregnant woman or even her attending physician. By the way, it is not at all necessary for all expectant mothers to perform a biochemical blood test in this case. Coupons are usually issued only to those who had a poor first screening, the second screening during pregnancy is of a clarifying nature.

It is imperative to undergo this examination also for women over 35-40 years old, and regardless of whether they have children of their own, suffering from alcoholism and (or) drug addiction, surviving a severe viral disease in the early stages of gestation, those who already have children with chromosomal pathology, with a closely related marriage, as well as taking medications that have a toxic effect on the fetus.

Facts such as IVF, multiple pregnancies, diabetes mellitus in the mother, too little or too large a woman's weight, and some bad habits can influence the accuracy of the results.

Screening of the 2nd trimester allows you to find out how the unborn child grows and develops. Is it necessary to undergo the procedure, because it is considered much easier than the 1st screening? Who is the examination indicated, and how many weeks is it carried out? What does a woman need to know about the diagnosis?

How long does it take

Such testing (screening) for expectant mothers began to be carried out relatively recently, since 2000. It includes an ultrasound examination and biochemical analysis taken from a vein. The first time a pregnant woman is examined from 10 to 13 weeks, the second screening is carried out from 16 to 20 weeks. The timing of more informative and accurate analyzes required for the second screening is from 16 weeks to 6 day 18 weeks. With ultrasound - from 19 to 22 weeks.

If the blood of the pregnant woman did not arouse suspicion during the first examination, then at the 2nd screening the doctor recommends to undergo only ultrasound diagnostics. The third time an ultrasound scan is done from 22 to 24 weeks, and it is mandatory. Although, if desired, the future mother can donate blood again and be tested in any laboratory at her own expense.

What screening shows in the second trimester

Having come for an ultrasound scan, a future mother can count on the following information:

condition of the placenta,
are there any pathologies in the cervix and appendages;
the amount of amniotic fluid;
the location of the fetus in the womb;
the size of the fetus (volume of the chest, abdomen, head, length of the spinal column and limbs);
how the main organ of the nervous system develops - the brain and spinal cord;
how the facial bones, eyes, nose are developed;
the state of the cardiac and vascular system;
whether internal organs develop correctly.

Be sure to do a second screening for women at risk:

parents who are relatives;
have suffered an infectious disease during gestation;
parents with a genetic disease in the family;
if the woman has had cases of stillbirth and spontaneous abortion;
if children with mental, nervous, genetic pathologies were born in the family;
if any disorder is detected at the first screening.

How to properly prepare for the study

After the first test, the 2nd pregnancy screening is unlikely to be a surprise.

You need to prepare for it, as you did the first time:

the day before donating blood, you must refrain from eating fatty, spicy, fried foods;
donate blood on an empty stomach, and drink water only with strong thirst;
avoid stress and anxiety that can negatively affect the results.

Ultrasound is performed without special training. It has no contraindications, is painless and non-invasive. Ultrasound diagnostics of prenatal screening is considered a modern highly informative and safe method for examining the condition of mother and child.

The pregnant woman lies down on the couch. The doctor smears the abdomen with gel and conducts a study with a special sensor through the skin. The patient receives the transcript and the results after a few minutes.

What does 2 screening include?

The second screening shows the presence or absence of risks of having a child with chromosomal defects. The main task of prenatal screening is to identify mothers who are at risk of giving birth to a baby with deviations and to examine them more thoroughly, for example, invasively. Based on the results of an in-depth examination, treatment will be prescribed or artificial termination of pregnancy will be proposed.

The second screening is called triple screening, as it includes 3 indicators:

Alpha-fetoprotein (or ACE) it is a protein produced by the liver and gastrointestinal tract of the embryo already from 3 weeks. It is responsible for transporting nutrients and protecting the fetus from estrogens produced by the mother's body for its own protection.
Chorionic gonadotropin (CG)- hormone actively synthesized by chorionic tissues after embryonic implantation. It is considered an important indicator of a healthy pregnancy as it regulates female hormones. For the 1st screening, the study of the level of the β-subunit of hCG is characteristic, since by the 10th week its amount increases maximally, and then gradually decreases. During the second screening, β-subunits and hCG are equally studied.
Free estriol- a hormone synthesized by the baby's liver and adrenal glands. It affects the condition of the uterus, placental circulation and the functioning of the woman's mammary glands.

In modern laboratories, a pregnant woman can do an additional analysis that reveals the amount of inhibin A. This is a female hormone, the indicators of which depend on the timing of pregnancy and the general condition of the fetus.

Normal indicators for weeks and decoding

When interpreting the analyzes done during screening, external factors are taken into account: weight, height of the pregnant patient, her bad habits.

Biochemical analysis standards

Week of pregnancy	HCG, IU / ml, thousand	ACE UNIT / ml	St. estriol nmol / l
16	10-58	15-95	5,5-20
17	8-57	15-95	6,5-25
18	8-57	15-95	6,6-25
19	7-49	15-95	7,5-27
20	1,6-49	27-125	7,6-27

Many patients who are carrying a child are interested in what they look at an ultrasound scan and how long it is best to do it. Experts believe that ultrasound diagnostics better done before 22 weeks... If there is an indication for termination of pregnancy, then a medical abortion after 23 weeks is not done. Then the pregnancy is interrupted by artificial childbirth.

Ultrasound standards

If the prenatal screening data correspond to standard norms, then the possibility of having a healthy baby is extremely high. But there is also a small percentage of error, in which even not quite comforting results indicate the presence of some kind of disorder. There are a number of factors that directly affect the results (this applies to biochemical analysis):

obesity, diabetes mellitus in mom;
multiple pregnancy;
addictions (, drug addiction);
conception by the IVF method.

Deviations from established norms

If factors that negatively affect screening are not identified, then overestimated or underestimated values may indicate some defects in the development of the fetus.

Index	High	Understated
Alpha-fetoprotein	- multiple pregnancy; - pathology of the nervous and digestive system; - congenital nephrotic syndrome;	- suspicion of the presence of Down syndrome or Edwards; - developmental delay in the womb; - frozen pregnancy
HCG	- various diseases of the mother; - gestosis; - taking hormonal medications; - suspicion of the presence of Down syndrome and Patau syndrome	- the risk of spontaneous abortion; - developmental delay in the womb; - the threat of Edwards syndrome
Free estriol	- multiple pregnancy; - Various diseases of the mother; - gestosis; - suspicion of Down syndrome and Patau syndrome	- the threat of Edwards syndrome and Down syndrome; - underdevelopment of the nervous system of the fetus; - complicated pregnancy; - taking illegal drugs while carrying a child
Inhibin A	- the possibility of giving birth to a child with chromosomal abnormalities; - cancerous growths; - placental insufficiency	- threat of self-abortion

Only the doctor is engaged in decoding the results of prenatal screening and explains to the patient her further actions.

For about 19 women, the doctor suggests a second screening and ultrasound. These terms were not chosen by chance: at this time, it is most convenient to study hormones. The first, as we remember, was in the middle of the 1st trimester of pregnancy. He usually shows that everything is fine. Indeed, at that time, it is only possible to determine with accuracy whether the fetus is developing correctly or not. Understanding what deviations from the norm mean at such a time is not easy. But on the 20th week, the screening results can tell a lot. So why is a second trimester screening worth it, and is it worth the money?

To begin with, not all diseases are the result of external influences. Simply put, you cannot shield a child from everything. There are diseases that begin in the first week of the intrauterine life of the fetus. For example, Down's syndrome, which is formed at the time of crossing of chromosomes, that is, even during conception. They are detected, for example, by screening or ultrasound. But nothing will help to avoid their appearance: here everything is in the hands of fate.

At the same time, raising a patient is not easy: not every family has the means and the desire to take care of a baby with such deviations, because this is not just a cold. It's not even a disability. These are completely different children who grow up as completely different people who will find it difficult to settle down in this world. And they will only have you, parents. It’s very difficult to accept that your child is “wrong”.

The results of the second screening and ultrasound performed during pregnancy give the parents-to-be a choice: if the child is sick, it is possible not to give birth. It's not too late to have an abortion. True, the reliability of such a study is not very high and it often turns out that the child was actually healthy.

But back to the topic of screening. Let's see what screening is, what is its essence, what are the types of screening.

Screening is from the English "sifting". That is, the definition of a risk group in which the appearance of children with certain diseases is possible. The calculation of probabilities can be done according to different principles. The most famous screening program is PRISCA (Prenatal RISk Assessment) - perinatal risk assessment.

Basic analyzes

The standard time for the 2nd screening is from 15 to 20 weeks of pregnancy. The later all examinations are carried out, the more accurate the results will be. But it is also more dangerous to have an abortion. Therefore, the optimal time for screening is 17-19 weeks of pregnancy. Your doctor will refer you to:

2nd trimester biochemical screening. He's a triple test. Here they will take blood from a vein and check three components (AFP, hCG, estriol) of the blood for the presence of special markers. So it will be clear what the risk of diseases such as Down syndrome or Edwards syndrome is. This type of screening is completely safe as there is no effect on the mother's body. The blood is simply being studied.

Screening ultrasound. It is more accurate than conventional ultrasound. With its help, it is possible to identify such disorders as heart disease, cleft of the upper lip or palate, diaphragmatic hernia, shortened bones, clubfoot, crossed fingers, etc. These can be both minor abnormalities that can be cured with time, medication or surgery, as well as serious defects that will remain with the child for life.

Cordocentesis... It is not required as part of the screening. But if any abnormalities were detected during an ultrasound scan or during an examination, this procedure is desirable. Here, using a special needle, fetal blood will be taken from the umbilical cord in order to conduct more detailed examinations and obtain more accurate results. This method is not completely safe. In 2% of cases, a woman has a miscarriage during pregnancy after this procedure. Often there are various hematomas and bleeding after the injection, but they go away rather quickly. In 1 case out of 100, an infection is introduced into the bloodstream.

Often, PRISCA includes examinations such as calculating cervical transparency (calculated through ultrasound), measuring the coccygeal-parietal size, and many others.

Possible diseases

Most often, perinatal screening of the 2nd trimester is carried out to find out if the child has some rare, but no less frustrating diseases during pregnancy.

Down Syndrome

As mentioned earlier, this disease appears even at the moment of chromosome crossing immediately after conception. Otherwise, Down's syndrome is called trisomy 21, that is, the 21st pair of chromosomes is not a pair, but a triplet. This is due to the fact that in the sperm or egg at the time of conception there was one extra 21st chromosome. The probability of this is approximately 1-1.5%.

The problem is that it is impossible to predict in advance the occurrence of this disease in a child. It practically does not depend on the woman and the child's father. The age of the mother only slightly affects the likelihood of the syndrome.

Neural tube defect

The neural tube forms in the embryo around the 20th day of pregnancy in the form of a plate. In a few more days, she should be curled up into a tube. These terms are not very long, so the process goes almost imperceptibly. The problem is that it may not close a cavity or unfold in the future, due to which defects of the spine may appear. Unfortunately, it is difficult to immediately determine this disorder at the beginning of pregnancy. By the middle of the 2nd trimester, that is, by the time of the 2nd screening, this defect can already be detected by ultrasound.

This disorder can result in spina bifida, hernia, and other neurological defects. The 2nd biochemical screening allows you to notice these defects.

Edwards syndrome

The causes of this disease are the same as those of Down's syndrome. Only here the trisomy of the 18th pair occurs. Such babies are born late, but outwardly they look like premature babies. They are small, light, painful and weak. Numerous defects of internal organs and body parts, which can be seen on ultrasound. Such a child will not live long: it is rare for a baby to live to see its first birthday.

Fortunately, this syndrome is extremely rare: in 1 case out of 5000. But the probability is still there.

Screening results

The screening examination should take place on the same day. Then the check and count will take place for several weeks, and only then the results will be ready. These are the terms. Biochemical screening of the 2nd trimester of pregnancy will show the level of three elements. What is the interpretation of the results?

This is a protein that the fetus itself produces, and not the mother's body during pregnancy. During the 2nd trimester screening, its percentage is accurately calculated. It enters the woman's bloodstream in certain quantities. Any deviation from the norm means some kind of abnormality in the development of the fetus.

According to PRISCA, at 15-19 weeks of gestation, the level should be approximately 15-95 U / ml. The doctor will tell you more.

If a biochemical screen or ultrasound shows that your results are higher than normal, it is likely that there is a developmental disorder of the spinal cord or a defect in the neural tube.

If the ACE level is much lower than normal, Down's or Edwards syndrome, Meckel's syndrome, occipital hernia, liver necrosis, spina bifida are possible. In this case, the 2nd screening is extremely imprecise. But even on an ultrasound scan, it is not easy to notice these deviations.