Echography in Obstetrics

Currently, echography is the leading method of obstetrics research. The use of modern equipment allows you to determine the pregnancy already at 4.5 weeks (counting from the 1st day of the last menstruation). During this period, the diagnosis of pregnancy is based on the detection of anehogenous formation (fetal egg) with a diameter of about 0.5 cm, surrounded by a hyperechoic ring of a villous chorion 0.1-0.15 cm thick. In 5-5.5 weeks, in most cases it is possible to obtain an embryo image , the coccyx-parietal size of which in these terms of pregnancy is 0.4 cm. At the same time, the cardiac activity of the embryo begins to be determined.

At 8 weeks, the fetal egg occupies almost half the volume of the uterus. In the same period, the villous chorion, previously uniformly covering the entire periphery of the fetal egg, thickens in a relatively small area and gives rise to the future placenta. At the same time, the rest of the chorion loses its villi, atrophies and turns into a smooth chorion.

In 9 weeks, the head of the embryo is visualized as a separate anatomical entity. In the same period, fetal movements appear for the first time, and 10 weeks begin to be determined by its limbs. Cardiac activity of the fetus undergoes changes in the early stages of pregnancy. At 5 weeks, the heart rate is 120-140 per minute, 6 weeks - 160-190 per minute, at the end of the first trimester of pregnancy - 140-60 per minute and is subsequently maintained at about the same level.

Term of pregnancy in the first trimester can be established based on the measurement of the average diameter of the fetal egg or the coccyx-parietal fetal size. To do this, use tables or special equations.

The average error in determining the gestation period for the measurement of the fetal egg is ± 5 days and KTP ± 2.2 days.

With multiple pregnancies in the uterine cavity, 2 fetal eggs and more (in the future, fruits) are found. It should be noted that not always a multiple pregnancy ends with the birth of several children. This is due to the fact that in a number of cases there is either a spontaneous miscarriage or an intrauterine death of one of the fetuses.

For an undeveloped pregnancy, a decrease in the size of the fetal egg in comparison with the expected duration of pregnancy, its deformation, thinning of the chorion is characteristic. Observe also fragmentation, disintegration of the fetal egg and indistinctness of its contours. In some cases, it is located in the lower parts of the uterus. Along with this, one can not register cardiac activity.

In a significant number of observations, the embryo in the uterus is absent (anembrionia). If anembrionia is detected after 7 weeks of gestation, it is inadvisable to keep the pregnancy. It should be noted that on the basis of only one echographic study, it is not always possible to diagnose an undeveloped pregnancy. Therefore, there is often a need for a second survey. The absence of an increase in the size of the fetal egg after 5-7 days confirms the diagnosis.

Threatening abortion occurs more often due to increased contractile activity of the uterus. Clinically manifested by pain in the lower abdomen and in the lower back. While maintaining the connection between the uterus and the fetal egg, the data of the echography usually do not differ from those of a normal pregnancy. In those cases when a fetal egg exfoliates from its bed, then between it and the wall of the uterus are found echoesfree spaces, indicating the accumulation of blood. With a significant detachment, a decrease in the rupture of the fetal egg and the death of the embryo are observed. Clinically, in these cases, the intensity of blood discharge from the genital tract is usually noted. The threat of interruption can also be indicated by shortening of the cervix to 2.5 cm or less, as well as the expansion of the cervical canal.

With incomplete abortion, the size of the uterus is much less than the expected duration of pregnancy. In the uterine cavity, small dense, increased echogenicity components or individual scattered echostructures are visible (the remains of the fetal egg and blood clots). At the same time, the fetal egg is not visualized. The uterine cavity is usually somewhat enlarged.

With complete miscarriage, the uterus is not enlarged. The uterine cavity either is not visualized, or has small dimensions. The absence of additional echostructures in it indicates a complete abortion. In these cases, there is no need for surgical intervention.

Bubble skidding is a rare complication, its prevalence is 1 case for 2000-3000 pregnancies. It occurs as a result of damage to the fetal egg and the transformation of the chorion into groinlike formations. They are transparent bubbles the size of millet grains to hazelnuts and more. These vesicles are filled with a liquid containing albumin and mucin.

Diagnosis of bladder skidding is based on the detection in the uterine cavity of multiple anechogenous echostructures of round or oval shape. In a significant number of observations within this formation, the appearance of echogenic zones of different sizes and forms, indicating the presence of blood, is noted. About 2/3 of the cases one-or two-sided multi-chamber fluid formations (teka-luteal cysts) are found. Their diameter varies from 4.5 to 8 cm. After removal of the bladder drift, these cysts gradually decrease in size and disappear. In doubtful cases, the definition of chorionic gonadotropin in the blood should be recommended, the concentration of which increases significantly in the presence of this pathology.

With ectopic pregnancy in the area of the appendages of the uterus, anechogenous formation of a rounded shape (fetal egg) is found, surrounded by a rim of the villous chorion. Its size approximately corresponds to the expected duration of pregnancy. Sometimes inside this formation one can see the embryo and establish its cardiac activity.

With a broken tubal pregnancy on the side of the uterus, a liquid formation of various sizes and shapes can be found containing multiple amorphous echostructures and a finely dispersed displaceable suspension (blood). In the case of rupture of the fetus, a free fluid is detected in the anterior space, and sometimes with profuse bleeding and in the abdominal cavity of the woman. It contains a displaceable finely dispersed suspension and amorphous ehostruktury. In the absence of bleeding in ectopic pregnancy, a thickened hyperechoic endometrium is detected, and in the presence of bleeding it is usually not detected, whereas the uterine cavity is enlarged.

The septum in the uterus is visible as a fairly thick formation, going in the anteroposterior direction. The partition can be either complete or incomplete. With an incomplete septum, the uterine cavity usually consists of two halves of different sizes. And in a significant number of cases, you can see that in one of its halves is the fruit, and in the other - the placenta. Ultrasound diagnosis of a complete septum presents great difficulties. On the scans in this pathology, in one half of the uterus, the fetal egg is determined, and in the other, the thickened endometrium.

The combination of pregnancy with intrauterine contraceptives is not uncommon. Since with the development of pregnancy the nylon thread is drawn into the uterine cavity, there may be an erroneous idea of the loss of the contraceptive. In the first trimester of pregnancy, the detection of intrauterine contraceptives does not present difficulties. Usually the contraceptive is extraamnial. On scans, intrauterine contraceptives are defined as hyperechoic formations of various forms, located mainly in the lower parts of the uterus. In the second half of pregnancy intrauterine contraceptive is not always visible. This is due, on the one hand, to its small size, and on the other hand to the fact that it is quite often "closed" by large parts of the fetal body.

Of the volume formations during pregnancy, the cyst of the yellow body is most often met. It is usually a 3-8 cm diameter formation with thick walls (0.2-0.5 cm). The internal structure of the cyst is very diverse. It can have a mesh, cobwebby inner structure, contain an irregularly shaped septum, various forms of tight inclusions, and also be completely filled with hyperechoic contents (blood). A characteristic feature of this cyst is that it gradually decreases in size and disappears within 1-3 months.

Important in the II and III trimesters is the establishment of the gestation period, the weight of the fetus, its growth and hypotrophy. For this, in bimetallic and frontal-occipital dimensions of the fetal head (D), the middle circumference of the abdomen (F), the length of the femoral (B), tibia, humeral (P) bones, feet, interhemispheric size of the cerebellum, mean transverse diameter of the heart [ (C) one of the sizes is determined from the pericardium to the pericardium, the other from the posterior pericardial wall to the end of the interventricular septum]. To determine these parameters, use special tables, nomograms, mathematical equations and computer programs.

In our country, the most widely spread tables, equations and programs developed by VN. Demidov and co-workers. Thus, the error in determining the duration of pregnancy when using computer programs developed by these authors turned out to be significantly less than when using the equations and programs proposed by other researchers. The average error in determining the gestational age when using a computer program was ± 3.3 days in the second trimester, ± 4.3 in the third trimester and ± 4.4 days in the case of hypotrophy.

To determine the weight (M) of the fetus in the III trimester of pregnancy, VN. Demidov et al. Suggested the following equation:

M = 33.44 × G ^{2 -} 377.5 × G + 15.54 × F ^{2 -} 109.1 × F + 63.95 × C ² + + 1.7 × C + 41.46 × B ^{2 -} 262 , 6 × B + 1718.

This equation gives quite satisfactory results, but the most reliable information can be obtained by using a computer program. It is also developed by these authors. The average error in determining the weight of the fetus when using this program was in the second trimester of pregnancy ± 27.6 g, in the second trimester ± 145.5 g and with its hypotrophy ± 89.0 g.

To determine the hypotrophy, the following equation can also be used (suggested by VN Demidov and co-authors):

K = (0.75 × GAcer + 0.25 × GAfoot - 0.25 × GAhead - 0.75 × GAabd) × 0.45 + 0.5,

Where GAcer is the gestation period for interhemispheric size of the cerebellum; GAfoot - term of pregnancy on the foot; GAhead - the gestation period for the average diameter of the head; Gаabd - the gestation period according to the average diameter of the abdomen.

In this case, the degree of hypotrophy (K) is determined as follows: degree of hypotrophy 0 (no hypotrophy) - K <1; degree I - 1 ≤ K <2; degree II - 2 ≤ K <3; degree III - 3 ≤ K. The accuracy of the definition of hypotrophy when using this equation is 92%, and its degree is 60%.

To detect markers of chromosomal pathology, echography is important. The most informative increase in the collar fetal space in the period of 11-14 weeks. It was found that the thickness of the collar space should not be more than 2.5 mm. Its increase (a thickness of 3 mm or more) is indicative of the presence of a chromosomal pathology in 1/3 of the cases. Most common: Down syndrome (approximately 50% of cases), Edwards syndrome (24%), Turner syndrome (10%), Patau syndrome (5%), other chromosomal pathology (11%). A fairly clear relationship is established between the thickness of the collar space and the frequency of chromosomal pathology. With a thickness of the collar space of 3 mm, genotype disorders occurred in 7% of the fetuses, 4 mm in 27%, 5 mm in 53%, 6 mm in 49%, 7 mm in 83%, 8 mm in 70%, and 9 mm - in 78%.

Certain information on the presence of chromosomal pathology can be measured by measuring the length of the nasal bones of the fetus. Normally, at 12-13 weeks, it should not be less than 4 mm, in 13-14 weeks - less than 4.5 mm, in 14-15 weeks - less than 5 mm. The length of the nose bones below these values may indicate a chromosomal pathology, most often of Down's syndrome.

The presence of Down syndrome in the second trimester of pregnancy can also indicate a shortening of the length of the femur of the fetus. Based on numerous studies, it was found that a decrease in length of the femur for 2 weeks or more, compared with the expected duration of pregnancy with Down's disease, is approximately 3.5 times more common than in the case of its physiological course.

Other markers of chromosomal pathology include cysts of cerebral vascular plexuses, hyperechoic intestine, hyperechoic formations on papillary muscles of the heart, minor hydronephrosis, shortening of tubular bones, umbilical cord cysts, constant retraction of the big toe, retardation of intrauterine development of the fetus.

In the presence of only one of these markers, the risk of chromosomal pathology remains almost the same as in the physiological course of pregnancy. However, if two or more markers are detected, the risk of its occurrence substantially increases. In these cases, amniocentesis or cordocentesis should be recommended for subsequent karyotyping.

In multiple pregnancy in the II and III trimesters, two or more fetuses are found. Doubles can be monozygotic (monochorionic) and bizhygotic (bichoric). The diagnosis of bizygotic twins is based on the detection of two separately located placentas, thickening of the dividing septum up to 2 mm or more, of unisexual fetuses. In 10-15% with monochorionic double fetofetal transfusion syndrome develops. Perinatal mortality in this case is 15-17%. The development of this syndrome is due to the presence of vascular anastomoses, leading to shunting of blood from one fetus to another. As a result, one fetus becomes a donor, the other a recipient. At the first one is observed anemia, developmental delay, lack of water, the second develops erythremia, cardiomegaly, non-immune dropsy, polyhydramnios.

Echography plays an important role in determining the volume of amniotic fluid. In the early stages of pregnancy amniotic membranes take part in the formation of amniotic fluid; in the second and third trimesters, their presence is due to urinary excretion of the fetus. Amounts of amniotic fluid are considered normal if the diameter of the deepest pocket is 3-8 cm. Reduction of the number of amniotic fluid is often observed with fetal hypotrophy, kidney and urinary system anomalies, and their complete absence - with renal agenesis. Polyhydramnios may be due to certain abnormalities of the gastrointestinal tract and infection of the fetus.

The use of echography in almost all cases allows you to establish a presentation (head, pelvic) and the position of the fetus (longitudinal, transverse, oblique).

To determine the condition of the cervix, the technique of a filled bladder is used or transvaginal echography is used. An ischemic-cervical insufficiency can be suspected if the length of the cervix is less than 25 mm or its proximal proximal part. The length of the cervical canal 20 mm to 20 weeks gestation can serve as an indication for suturing the cervix.

The sex of the fetus in a significant number of observations can be established as early as 12-13 weeks. In the early stages of pregnancy, the penis is defined as a small formation resembling an arrowhead. For a female fetus, it is characteristic to find three hyperechoic parallel linear strips on the scans. After 20 weeks, the sex of the fetus is determined in almost all observations.

Echography is important in identifying the developmental defects of the fetus. The optimal timing of echographic screening for determining fetal development abnormalities: 11-13, 22-24, 32-34 weeks gestation.

Carrying out echographic screening in the first trimester can detect only about 2-3% of developmental abnormalities. This group, as a rule, includes coarse malformations: anencephaly, acrania, ectopia of the heart, omphalocele (umbilical hernia), gastroschisis (defect of the anterior abdominal wall with exit of the abdominal cavity to the outside), undivided twins, complete atrioventricular block, cystic lymphangioma of the neck and etc.

Due to the fact that the defects usually diagnosed during this period are incompatible with the extrauterine life, in most cases the pregnancy is interrupted.

In the II and III trimesters, it is possible to determine the majority of malformations as a violation of the anatomical structure of individual organs and fetal systems. In specialized institutions, the accuracy of their diagnosis reaches 90%.

The main reasons for the erroneous results of malformations include inadequate medical qualifications, imperfect ultrasound equipment, unfavorable for the study of the fetal position, marked low blood pressure, increased development of subcutaneous fat.

The rational tactics of managing pregnancy, the choice of the method of delivery and the further tactics of treating the fetus and the newborn are extremely important, taking into account the nature of the revealed pathology. For this purpose, several groups of fetuses and newborns have been identified.

• Group 1. Pathology, which can be surgically corrected during pregnancy: diaphragmatic hernia, hydrothorax, sacrococcygeal teratoma, urinary tract obstruction, aortic and pulmonary artery stenosis, transfusion syndrome in multiple pregnancy, amniotic tracts.
• Group 2. Pathology requiring urgent surgical treatment: umbilical hernia, gastroschisis, atresia of the esophagus, duodenum, small and large intestine, unperforated anus, diaphragmatic hernia, cystic adenomatosis of the lung, leading to respiratory failure, severe heart defects, massive intrapartum intracranial hemorrhages.
• Group 3. Pathology requiring hospitalization in the surgical department during the neonatal period: volumetric abdominal cavity, pulmonary sequestration, multicystosis of the kidney, megaureter, hydronephrosis, bladder exstrophy, sacral region teratoma, lymphangioma of the neck, heart defects with circulatory disturbances, cleft lip and palate, hydrocephalus, meningocele of the brain and spinal cord, tumors and cysts of the brain.
• Group 4. Pathology requiring delivery by cesarean section. Giant teratoma, omphalocele, gastroschisis, lymphangioma of the neck of large sizes, undivided twins.
• Group 5. Pathology that gives grounds for discussing the issue of termination of pregnancy: polycystic kidneys of an adult type, achondroplasia, a valve of the posterior urethra in combination with a bilateral megaureter, hydronephrosis and megacystis, cystic renal dysplasia, severe hypoplasia of both kidneys, gross disabling limb anomalies, crevices of the face, microphthalmia, anophthalmia.
• Group 6. Pathology requiring abortion: anencephaly, holoproencephaly, hydrocephalus due to Arnold-Chiari syndrome, exsencephaly, large-sized cranial and spinal hernias, facial cleavage, agenesis of the eyeballs, gross heart defects, ectopia of the heart, life-incompatible skeletal defects , arteriovenous anomalies of the central nervous system, cavernous hemangioma and some other malformations of the brain.
• Group 7. Pathology requiring clinic observation: agenesis of the corpus callosum, small cysts of the brain, vitreous heart defects, cysts of the abdominal cavity and retroperitoneal space, solitary lung cysts, cystic adenomatosis of the lungs without the phenomena of respiratory failure, joint deformity, inguinal and scrotal hernia , edema of the testicles, cystic ovarian formations, heart defects without circulatory disturbance, cardiomyopathy.

It should be noted that in most cases antenatal surgical correction is not a radical method. It creates basically only conditions for more favorable development of the fetus or preservation of the affected organ before the term of labor and subsequent treatment in the period of newborn. 40-50% of congenital malformations of the fetus are amenable to a successful correction in case of timely conduction.

One of the important aspects of the application of ultrasound is the study of the placenta. The application of this method allows you to establish a presentation, premature detachment, find an additional fraction, determine the thickness and diagnose various volumetric formation of the placenta.

It has been established that a decrease in the thickness of the placenta is observed more often in fetoplacental insufficiency and polyhydramnios, and its increase in immunoconflict pregnancy and diabetes.

In addition, the use of echography makes it possible to detect intervosse thrombi, infarcts, sub-menic cysts and placenta chorioniomas, which is important in determining the further tactics of pregnancy management.

Thus, the presented data indicate that echography is a valuable method that allows obtaining important information. Its use can contribute to a significant reduction in adverse outcomes for both the mother and the fetus.

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