Echography in obstetrics

Currently, echography is the leading method of obstetrics research. The use of modern equipment allows to establish pregnancy already at the term of 4.5 weeks (counting from the 1st day of the last menstruation). During this period, pregnancy diagnostics is based on the detection of an anechoic formation (fertilized egg) with a diameter of about 0.5 cm, surrounded by a hyperechoic ring of villous chorion with a thickness of 0.1–0.15 cm. At 5–5.5 weeks, in most cases, it is possible to obtain an image of the embryo, the coccygeal-parietal size of which at these stages of pregnancy is 0.4 cm.

At 8 weeks, the fertilized egg occupies almost half of the uterus. During this same period, the villous chorion, which previously uniformly covered the entire periphery of the fertilized 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.

At 9 weeks, the embryo's head is visualized as a separate anatomical formation. During this period, fetal movements first appear, and at 10 weeks, its limbs begin to be defined. The fetal cardiac activity undergoes changes in the early stages of pregnancy. At 5 weeks, the heart rate is 120-140 per minute, at 6 weeks - 160-190 per minute, at the end of the first trimester of pregnancy - 140-60 per minute and subsequently remains at approximately the same level.

The gestational age in the first trimester can be determined based on the measurement of the average diameter of the ovum or the crown-rump length of the fetus. For this, tables or special equations are used.

The average error in determining the gestational age when measuring the ovum is ±5 days and CTE±2.2 days.

In multiple pregnancies, 2 or more fertilized eggs (and subsequently fetuses) are found in the uterine cavity. It should be noted that multiple pregnancies do not always result in the birth of several children. This is due to the fact that in some cases, either a spontaneous miscarriage or intrauterine death of one of the fetuses occurs.

A non-developing pregnancy is characterized by a decrease in the size of the fertilized egg compared to the expected gestational age, its deformation, and thinning of the chorion. Fragmentation, disintegration of the fertilized egg, and blurring of its contours are also observed. In some cases, it is located in the lower parts of the uterus. Along with this, cardiac activity cannot be registered.

In a significant number of observations, the embryo is absent from the uterus (anembryony). If anembryony is detected after 7 weeks of gestation, it is not advisable to continue the pregnancy. It should be noted that based on only one ultrasound examination, it is not always possible to diagnose a non-developing pregnancy. Therefore, a repeated examination is often necessary. The absence of an increase in the size of the ovum after 5-7 days confirms the diagnosis.

Threatened abortion often occurs due to increased contractile activity of the uterus. Clinically, it is manifested by pain in the lower abdomen and lower back. If the connection between the uterus and the fertilized egg is maintained, the echographic data usually do not differ from those in a normal pregnancy. In cases where the fertilized egg separates from its bed, echo-free spaces are found between it and the uterine wall, indicating blood accumulation. With significant detachment, a decrease in ruptures of the fertilized egg and death of the embryo are observed. Clinically, in these cases, bloody discharge from the genital tract of varying intensity is usually noted. A shortening of the cervix to 2.5 cm or less, as well as an expansion of the cervical canal, may also indicate a threat of termination.

In case of incomplete abortion, the size of the uterus is significantly smaller than the expected gestational age. Small dense, high-echo components or separate scattered echostructures (remnants of the fertilized egg and blood clots) are visible in the uterine cavity. At the same time, the fertilized egg is not visualized. The uterine cavity is usually somewhat dilated.

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

Hydatidiform mole is a rare complication, with an incidence of 1 in 2,000–3,000 pregnancies. It occurs when the ovum is damaged and the chorion is transformed into grape-like structures. They are transparent bubbles the size of a millet grain to a hazelnut or larger. These bubbles are filled with fluid containing albumin and mucin.

Diagnosis of hydatidiform mole is based on the detection of multiple anechoic echostructures of round or oval shape in the uterine cavity. In a significant number of observations, echogenic zones of different sizes and shapes are observed inside this formation, indicating the presence of blood. In approximately 2/3 of cases, unilateral or bilateral multi-chamber fluid formations (theca-lutein cysts) are detected. Their diameter ranges from 4.5 to 8 cm. After removal of the hydatidiform mole, these cysts gradually decrease in size and disappear. In doubtful cases, it is recommended to determine the chorionic gonadotropin in the blood, the concentration of which increases significantly in the presence of this pathology.

In case of ectopic pregnancy, an anechoic formation of a round shape (fertilized egg) surrounded by a rim of villous chorion is found in the area of the uterine appendages. Its size approximately corresponds to the expected gestational age. Sometimes, an embryo can be seen inside this formation and its cardiac activity can be determined.

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

The uterine septum is visible as a rather thick formation running in the anteroposterior direction. The septum can be either complete or incomplete. With an incomplete septum, the uterine cavity usually consists of 2 halves of different sizes. Moreover, in a significant number of cases, it can be seen that the fetus is located in one of its halves, and the placenta in the other. Ultrasound diagnostics of a complete septum presents great difficulties. On scanograms with this pathology, a fertilized egg is determined in one of the halves of the uterus, and a thickened endometrium in the other.

The combination of pregnancy with intrauterine contraceptives is not uncommon. Since the nylon thread is drawn into the uterine cavity as the pregnancy progresses, a false impression of the loss of the contraceptive may arise. In the first trimester of pregnancy, detection of intrauterine contraceptives is not difficult. Usually, the contraceptive is located extra-amniotically. Intrauterine contraceptives are defined on scanograms as hyperechoic formations of various shapes, located mainly in the lower parts of the uterus. In the second half of pregnancy, the 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 often "covered" by large parts of the fetus's body.

Of the volumetric formations during pregnancy, the most common is the corpus luteum cyst. It is usually a formation with a diameter of 3-8 cm with thick walls (0.2-0.5 cm). The internal structure of the cyst is very diverse. It can have a mesh, arachnoid internal structure, contain irregularly shaped partitions, dense inclusions of various shapes, 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.

In the second and third trimesters, it is important to determine the gestational age, fetal weight, growth and hypotrophy. For this purpose, the biparietal and fronto-occipital dimensions of the fetal head (G), average abdominal circumference (G), length of the femur (B), tibia, humerus (H), foot, interhemispheric size of the cerebellum, average transverse diameter of the heart [(C) one of the dimensions is determined from the pericardium to the pericardium, the other - from the far wall of the pericardium to the end of the interventricular septum] are measured in centimeters. Special tables, nomograms, mathematical equations and computer programs are used to determine these parameters.

In our country, the tables, equations and programs developed by V.N. Demidov et al. have become the most widely used. Thus, the error in determining the gestational age using the computer programs developed by these authors turned out to be significantly smaller than when using the equations and programs proposed by other researchers. The average error in determining the gestational age using the computer program was ±3.3 days in the second trimester, ±4.3 in the third trimester and ±4.4 days in case of hypotrophy.

To determine the mass (M) of the fetus in the third trimester of pregnancy, V.N. Demidov et al. proposed using 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 using a computer program. It was also developed by these authors. The average error in determining the fetal weight using this program was ±27.6 g in the second trimester of pregnancy, ±145.5 g in the second trimester, and ±89.0 g in its hypotrophy.

The following equation (proposed by V.N. Demidov et al.) can also be used to determine hypotrophy:

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

Where GАcer is the gestational age according to the interhemispheric size of the cerebellum; GAfoot is the gestational age according to the foot; GАhead is the gestational age according to the average diameter of the head; Gаabd is the gestational age according to the average diameter of the abdomen.

In this case, the degree of hypotrophy (K) is determined as follows: degree of hypotrophy 0 (absence of hypotrophy) - K < 1; degree I - 1 ≤ K < 2; degree II - 2 ≤ K < 3; degree III - 3 ≤ K. The accuracy of determining hypotrophy using this equation is 92%, and its degree - 60%.

Echography is important for detecting markers of chromosomal pathology. The most informative is the increase in the nuchal translucency of the fetus at 11-14 weeks. It has been established that the thickness of the nuchal translucency should not normally exceed 2.5 mm. Its increase (thickness of 3 mm or more) approximately indicates the presence of chromosomal pathology in 1/3 of cases. The most common are: Down syndrome (approximately 50% of cases), Edwards syndrome (24%), Turner syndrome (10%), Patau syndrome (5%), and other chromosomal pathology (11%). A fairly clear relationship has been established between the thickness of the nuchal translucency and the frequency of chromosomal pathology. With a nuchal translucency thickness of 3 mm, genotype abnormalities were found in 7% of 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 about the presence of chromosomal pathology can be provided by measuring the length of the nasal bone of the fetus. Normally, at 12–13 weeks it should not be less than 4 mm, at 13–14 weeks – less than 4.5 mm, at 14–15 weeks – less than 5 mm. The length of the nasal bones below these values may indicate chromosomal pathology, most often Down syndrome.

The presence of Down syndrome in the second trimester of pregnancy may also be indicated by a shortening of the length of the femur of the fetus. Based on numerous studies, it has been established that a decrease in the length of the femur by 2 weeks or more compared to the expected gestational age in Down syndrome occurs approximately 3.5 times more often than in its physiological course.

Other markers of chromosomal pathology include cysts of the choroid plexus of the ventricles of the brain, hyperechoic intestine, hyperechoic formations on the papillary muscles of the heart, minor hydronephrosis, shortening of the tubular bones, umbilical cord cysts, permanent abduction of the big toe, and intrauterine growth retardation of the fetus.

If only one of the above markers is present, the risk of chromosomal pathology remains practically the same as during a physiological pregnancy. However, if two or more markers are detected, the risk of its occurrence increases significantly. In these cases, amniocentesis or cordocentesis should be recommended for subsequent karyotyping.

In multiple pregnancies, two or more fetuses are detected in the second and third trimesters. Twins can be monozygotic (monochorionic) and dizygotic (bichorial). The diagnosis of dizygotic twins is based on the detection of two separately located placentas, thickening of the dividing septum up to 2 mm or more, and fetuses of different sexes. In 10–15% of monochorionic twins, 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. The first has anemia, developmental delay, oligohydramnios, 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 participate in the formation of amniotic fluid; in the second and third trimesters, their presence is due to fetal urination. The amount of amniotic fluid is considered normal if the diameter of the deepest pocket is 3–8 cm. A decrease in the amount of amniotic fluid is often observed in fetal hypotrophy, kidney and urinary system anomalies, and their complete absence is observed in renal agenesis. Polyhydramnios may occur with some anomalies of the gastrointestinal tract and fetal infection.

The use of ultrasound in almost all cases allows us to determine the presentation (cephalic, breech) and position of the fetus (longitudinal, transverse, oblique).

To determine the condition of the cervix, the filled bladder technique or transvaginal echography is used. Isthmic-cervical insufficiency can be suspected if the length of the cervix is less than 25 mm or its proximal section is expanded. A cervical canal length of 20 mm before 20 weeks of pregnancy may serve as an indication for suturing the cervix.

The sex of the fetus can be determined in a significant number of observations as early as 12–13 weeks. In early pregnancy, the penis is defined as a small formation resembling an arrowhead. A female fetus is characterized by the detection of three hyperechoic parallel linear stripes on scanograms. After 20 weeks, the sex of the fetus is determined in almost all observations.

Echography is important in identifying fetal malformations. The most optimal time for conducting echographic screening to determine fetal malformations is 11–13, 22–24, and 32–34 weeks of pregnancy.

Conducting echographic screening in the first trimester allows detecting only about 2-3% of developmental anomalies. This group usually includes gross defects: anencephaly, acrania, ectopia cordis, omphalocele (umbilical hernia), gastroschisis (anterior abdominal wall defect with abdominal organs coming out), unseparated twins, complete atrioventricular block, cystic lymphangioma of the neck, etc.

Since the defects usually diagnosed during this period are incompatible with extrauterine life, in most cases the pregnancy is terminated.

In the second and third trimesters, it is possible to identify most developmental defects in the form of a violation of the anatomical structure of individual organs and systems of the fetus. In specialized institutions, the accuracy of their diagnosis reaches 90%.

The main reasons for erroneous results of developmental defects include insufficient qualifications of the doctor, imperfect ultrasound equipment, unfavorable position of the fetus for examination, severe oligohydramnios, and increased development of subcutaneous fat.

Of extreme importance is rational tactics of pregnancy management, choice of the method of delivery and further tactics of treatment of the fetus and newborn taking into account the nature of the identified pathology. For this purpose, several groups of fetuses and newborns have been identified.

• Group 1. Pathology for which surgical correction is possible during pregnancy: diaphragmatic hernia, hydrothorax, sacrococcygeal teratoma, urinary tract obstruction, aortic and pulmonary artery stenosis, transfusion syndrome in multiple pregnancies, amniotic bands.
• Group 2. Pathology requiring immediate surgical treatment: umbilical hernia, gastroschisis, atresia of the esophagus, duodenum, small and large intestines, imperforate 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 in the neonatal period: space-occupying lesions of the abdominal cavity, pulmonary sequestration, multicystic kidney disease, megaureter, hydronephrosis, bladder exstrophy, sacral teratoma, lymphangioma of the neck, heart defects with circulatory disorders, 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, large lymphangioma of the neck, conjoined twins.
• Group 5. Pathology that provides grounds for discussing the issue of termination of pregnancy: adult-type polycystic kidney disease, achondroplasia, posterior urethral valve in combination with bilateral megaureter, hydronephrosis and megacystis, cystic dysplasia of the kidneys, severe hypoplasia of both kidneys, gross disabling anomalies of the limbs, facial clefts, microphthalmia, anophthalmia.
• Group 6. Pathology requiring termination of pregnancy: anencephaly, holoprosencephaly, hydrocephalus caused by Arnold-Chiari syndrome, exencephaly, large cranial and spinal hernias, cleft face, agenesis of the eyeballs, severe heart defects, ectopia cordis, skeletal defects incompatible with life, arteriovenous anomalies of the central nervous system, cavernous hemangioma and some other malformations of the brain.
• Group 7. Pathology requiring dispensary observation: agenesis of the corpus callosum, small cysts of the brain, curable heart defects, cysts of the abdominal cavity and retroperitoneal space, solitary cysts of the lungs, cystic adenomatosis of the lungs without signs of respiratory failure, joint deformation, inguinal-scrotal hernias, hydrocele of the testicles, cystic formations of the ovaries, heart defects without circulatory disorders, cardiomyopathy.

It should be noted that in most cases, antenatal surgical correction is not a radical method. It mainly creates conditions for more favorable development of the fetus or preservation of the affected organ until the term of delivery and subsequent treatment in the neonatal period. 40-50% of congenital defects of the fetus can be successfully corrected if it is carried out in a timely manner.

One of the important aspects of using ultrasound is examining the placenta. Using this method allows you to establish presentation, premature detachment, detect an additional lobe, determine the thickness and diagnose various volumetric formations of the placenta.

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

In addition, the use of echography makes it possible to detect intervillous thrombi, infarctions, subamniotic cysts and chorionangiomas of the placenta, which is important in determining further pregnancy management tactics.

In summary, the data presented indicate that sonography is a valuable method that provides important information. Its use may contribute to a significant reduction in adverse outcomes for both mother and fetus.

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