Monitoring objective indicators of fetal status by ultrasound scanning

The possibilities of the ultrasonic method are as follows:

Determining the position of the fetus and the presenting part. Difficulties in determining the presenting part are usually observed in obese women, with polyhydramnios, with strong and frequent contractions. In such situations, with a high-standing head, even a vaginal examination does not resolve doubts.

Fetal biometry. Prenatal determination of fetal weight is of great importance for the doctor conducting the birth. Knowing the expected fetal weight is especially important in breech presentation, if there are indications for early termination of pregnancy. For this, there is a method proposed by A. V. Rudakov, which, unfortunately, in polyhydramnios and obesity gives a large number of diagnostic errors.

To estimate the fetal weight using ultrasound, it is necessary to measure the biparietal size of the head quite accurately. This size was chosen as a reference point because it is the most informative. Firstly, the ratio of the biparietal size to the fetal weight has the most constant numerical values compared to the other determined sizes; secondly, the bones of the skull are located parallel only in the temporoparietal region at a relatively large distance, and therefore a clear image of the oval is obtained. We used seven formulas, of which we chose the most reliable.

With small fruit sizes, the predicted weight, as a rule, turned out to be greater than the actual weight; with large fruits, the opposite relationship was observed, i.e. it should be remembered that with small fruits, their true weight is greater than the predicted weight, with large fruits, it is less. The decisive factor in determining the weight of the fruit is not the nature of the measured parameters, but the accuracy of the measurements; with fruits weighing up to 4000 g, careful measurement of the biparietal diameter allows for a sufficiently accurate weight prediction. The issues of predicting the weight of large fruits require further development.

Determining the relationship between the fetal head size and the maternal pelvis size. Using the ultrasound method, it is possible to simultaneously see the symphysis and promontory, thereby measuring the true conjugate with a high-standing head. By measuring the biparietal size of the head later, it is possible to estimate the probability of a discrepancy between the maternal pelvis and the fetal head size. This is especially important to know in the case of breech presentation of the fetus or diabetes mellitus in the mother, when even a small degree of discrepancy can lead to severe trauma to the fetus and newborn child or stillbirth.

Definition of multiple pregnancy. The diagnosis of multiple pregnancy during labor is significantly less important than during pregnancy. Ultrasound examination is the most accurate method of diagnosing multiple pregnancy; starting from 6 weeks, echography establishes multiple pregnancy in 100%. It allows not only to perform early diagnosis of multiple pregnancy, but also to determine the nature of fetal development by biometric indicators, the number of placentas (mono- or dichorionic placentation type) and amniotic cavities (mono- or diamniotic twins).

Ultrasound examination allows differentiating multiple pregnancy from polyhydramnios, hydatidiform mole and large fetus. The most optimal method of organizing early diagnostics of multiple pregnancy is ultrasound diagnostics (screening), i.e. mass examination of all women in a certain region at 16-20 weeks of pregnancy, which allows simultaneous detection of fetal developmental abnormalities, placenta localization, etc.

Timely determination of the position of the fetuses is indicated in terms of determining indications for cesarean section (transverse position, breech presentation, etc.).

In the past, the main method of diagnosing multiple pregnancy in unclear cases was X-ray, as well as phono- and electrocardiography of the fetuses. The first method is to some extent undesirable, and the second is not informative enough and can be used mainly in the late stages of pregnancy.

Definition of polyhydramnios. Polyhydramnios is physiological for the beginning of the second trimester of pregnancy. With pronounced polyhydramnios, it is difficult to determine the gestational age, the size of the fetus and the presence of developmental defects. Diagnostics is based on the detection of a large zone without reflections on the echogram between the uterine wall and the fetus; the image of the fetal parts and the head is located unusually freely at some distance from the image of the body.

Determination of fetal development anomalies. It is difficult to overestimate the importance and necessity of the earliest possible prenatal diagnosis of pronounced fetal development anomalies. In such situations, pregnancy should be terminated early, especially in cases where it is complicated. With timely diagnosis of anomalies, it is possible to save a woman from a number of surgical interventions during childbirth, especially - cesarean section. With the help of ultrasound, defects of the skull bones, as well as other fetal developmental defects (fetal ascites, polycystic kidney disease, fetal abdominal tumors, genitourinary system anomalies, etc.) are diagnosed quite reliably.

Anencephaly is best detected in the longitudinal plane, since in the transverse position the image of the skull base can imitate the circular image of the head. It is important to obtain an image of the skull base, after which the abnormal configuration of the head is easily detected. In such cases, polyhydramnios is often detected.

To diagnose hydrocephalus, it is necessary to determine the biparietal size of the head; its minimum value for making a diagnosis in full-term pregnancy is 11 cm. In addition, when comparing the sizes of the head and chest, a disproportion is determined. On the same basis, a diagnosis of microcephaly is established.

Determination of the location of the placenta. The normal duration of the labor act, the low percentage of labor-enhancing therapy, the lower frequency of surgical interventions during labor, pathological blood loss in the afterbirth and early postpartum periods and the birth of children in a state of hypoxia with the localization of the placenta in the body of the uterus allow us to consider this type of its location as the most favorable. It is recommended that when women in labor with the localization of the placenta in the bottom of the uterus have a combination of weakness of labor with other obstetric or extragenital pathology, the question of delivery by cesarean section should be raised in a timely manner.

When using the ultrasound method, the diagnosis is established based on the following signs:

• between the fetus and the uterine wall, many point additional echo signals are detected;
• the image of the edge of the placenta facing the fetus has a broken line (reflection from the chorionic plate), especially when the placenta is located on the anterior wall. At the same time, the degree of maturity of the placenta is determined. Based on the change in the echogenicity of the villous chorion at different stages of pregnancy, 3 stages of maturity are distinguished. In an uncomplicated pregnancy, each stage corresponds to a certain period (stage I - 12-31 weeks, stage II - 32-36 weeks, stage III - 37-40 weeks). In toxicosis of pregnancy, half of them have a discrepancy between the echogenicity of the chorion (acoustic density) and the gestational age. For severe toxicosis of pregnancy, a premature decrease in the echogenicity of the chorion is most characteristic.

The main indications for placentography are:

• Suspected placenta previa. Its image is especially clear with a full bladder and a high-standing presenting part (head), if the placenta is not located on the back surface of the uterus;
• Suspected premature detachment of a normally located placenta. The success of diagnosis depends on the degree of placental abruption;
• In the presence of scars on the uterus after surgical interventions, if the placenta is located on the anterior wall of the uterus, i.e. in the area where there is a scar. In these women, signs of scar failure are often detected during childbirth.

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