Ultrasound examination (ultrasound) in the 3rd trimester of pregnancy

After the 30th week of pregnancy, the unborn child begins to grow in the mother’s body at a double rate. At the same time, this pace applies to both the physical aspect of growth and the mental one. During this period of time, the expectant mother begins to easily distinguish with the movements of the child of his limbs, he greatly gains weight, the presentation of the fetus is finally determined. During this period, it is very important to monitor the condition and development of the child at screenings. On an ultrasound examination of the third trimester of pregnancy, specialists monitor the correct development of all organs of the baby.

What is the third screening for?

Ultrasound in the third trimester, as a rule, is carried out for a period from the 30th to the 32nd week. Occasionally, if there is a medical indication, screening can be done at 29 weeks, but due to the ambiguity of its results, the study will need to be repeated in the future. The main subjects for consideration of this ultrasound are such moments as the position or presentation of the child, the volume of amniotic fluid, the occurrence of cord entanglement, the degree of maturation of the placenta, the weight of the child at the time of screening.

The intrauterine presentation of the child is very important for future births. The head-down position is considered normal, but there are often cases when the fetus is located down the buttocks or even lies across the mother’s abdomen. In the case of diagnosing presentation in the third trimester of pregnancy, experts give only a few weeks for the position of the fetus to change to the correct one, otherwise doctors exclude natural childbirth, since they can be dangerous for both the mother and the child. Sometimes modern medicine allows natural childbirth with the breech presentation of the fetus, but with the condition that the woman in labor will be in a certain maternity hospital, where there are all the means and resources for effective caesarean section and resuscitation procedures for both the child and the mother.

In the third trimester of pregnancy, many women are referred for conservation due to oligohydramnios or polyhydramnios. Both of these situations can be very dangerous for the baby, since a change in the normal amount of amniotic fluid is almost always evidence of an intrauterine infection.

In the third trimester, the entanglement of the umbilical cord of the child is clearly visible. It happens that the fetus wraps around twice. Diagnosing this condition on ultrasound helps specialists decide on a caesarean section so that the fetus does not suffocate in the loops of the umbilical cord at birth. However, sometimes such a prescription simply needs to be brought to the attention of the doctor who will deliver the baby. With the appropriate qualifications of a specialist and a single loose entanglement, natural childbirth can be quite successful.

In order to avoid preterm birth, the degree of maturity of the placenta is necessarily determined at the third screening. With its early maturation or discrepancy between the maturity of the placenta and the terms at which the pregnancy is at the moment under study, they try to observe the expectant mother very closely. In this situation, it is important to ensure that all the necessary nutrients are delivered to the baby through the placenta.

At the 30th week, during an ultrasound examination, doctors make a presumptive conclusion about the possible weight with which the baby will be born. These conclusions are very approximate, but they are important if the woman in labor has a narrow pelvis, and the fetus is expected to be large. In this case, specialists also decide on a caesarean section.

All of the above indicators are not the only ones, but the most important for future childbirth and women, therefore, all data from such studies must be discussed between the doctor and the expectant mother in order to make an adequate decision regarding the delivery itself.

Study of fetometric data

During the ultrasound examination of the third trimester, specialists pay much attention to measuring the fetometric data of the unborn baby. Doctors measure the circumference of the head, the length of the femur, the circumference of the tummy. Thus, it becomes possible to specify the gestational age. If at least one small deviation from the norm occurs, the specialist begins to measure other parameters. When a number of deviations are established, extended fetometry is performed, including:

• measurement of the fronto-occipital part of the child’s head;
• measuring the ratio of a number of measured indicators;
• more accurate measurement of the circumference of the abdomen;
• measurement of the ratio between the circumference in the tummy and the length of the femurs.

When all of the above measurements are completed, the specialist will begin to consider the state of the fetal brain. Here, the choroid plexuses, the size of the lobes of the brain, and the dimensions of the cerebellum are very important aspects. All these data help doctors to exclude brain diseases in a child, to be sure that there are no intrauterine infections, which can subsequently cause very serious pathologies in human development. It is also important to consider the structure of the child’s face. Here, the parameters may indicate the absence of multiple developmental pathologies, which, ideally, should be diagnosed at the first screening.

The child’s spine is carefully studied in the context of each individual vertebra, in which the spinous process must be present, indicating the absence of pathological processes in this area.

Consideration of the state of the internal organs of the child

When conducting ultrasound in the third trimester of pregnancy, doctors will definitely diagnose the occurrence of malformations in the internal organs of a person. The most important internal organs in this consideration are the lungs and heart of the child. With underdevelopment of the diaphragm, doctors can also diagnose underdevelopment of the lung tissue, which in the future can lead to breathing problems. When considering the heart, all possible functional abilities of the ultrasound technique are used to examine in detail the presence of valves, septa and vessels, their size and functionality.

The organs in the abdominal cavity of the baby are considered no less carefully. From any pathology that occurs during pregnancy, in the first place, the kidneys of the child may suffer. Deviations in the size and shape of this organ always signal the presence of a disease. However, for the integrity of the picture, it is important to diagnose other organs of the abdominal cavity – the stomach, liver, intestines can also tell a lot about the doctor.

Sometimes, when a deviation in fetal development is detected on ultrasound within one week, we can talk about the incorrect determination of the timing of pregnancy by a gynecologist. If, with each subsequent study, the deviation remains within the same limits, then this is not given much importance, since with a high degree of probability, this fact indicates precisely the incorrectly set delivery date. But with a constant change in the deviation of indicators from a given period, doctors consider it necessary to sound the alarm and observe the pregnancy in more detail.

Consideration of the state of the placenta and uterus on ultrasound

Much attention is paid by ultrasound specialists to the condition of the placenta and uterus, since the health and proper development of these organs is the key to the success of a successful birth. Normally, the absence of deviations is characterized by:

• the establishment of a head intrauterine presentation in a child;
• the first stage of placental maturity;
• the absence of death of areas inside the placenta (placental infarcts);
• the absence of hematomas (otherwise the woman in labor is admitted to the hospital);
• the absence of tissue detachments, which may mean the onset of preterm labor;
• a normal amount of amniotic fluid with epithelial cells present in them;
• closure of both external and internal os;
• the size of the cervix is ​​at least 30 centimeters.

It happens that some deviations are considered normal by doctors. In such cases, no additional studies of the pregnant woman are prescribed. If the normal corridor of deviations is exceeded, a woman in labor can be sent both to a hospital for treatment and for additional examinations in order to identify and eliminate all emerging pathologies.

Consideration of the state of arteries and vessels in the framework of ultrasound

Intrauterine growth retardation, along with other causes, can also occur due to blood flow disorders and problems of the vascular system. Pathologies of these processes can slow down the nutrition of the child, which leads to inhibition of its normal development and growth.

Diagnosis of blood vessels during the third trimester of pregnancy is carried out by using another research technique – dopplerography, where all the main arteries responsible for delivering nutrients from mother to child are visualized and well studied. If a weakening of blood flow is detected in such arteries, mandatory treatment is prescribed.

The Doppler ultrasound sensor does not affect the child in any way, so this procedure, if necessary, is carried out repeatedly with a difference of a week. If deviations are not visualized during Dopplerography and other indicators of the infant’s viability are within the normal range, doctors believe that the existing features of the blood flow indicate the characteristics of a particular organism and are not pathologies.

Diagnosis of fetal diseases

When conducting an ultrasound examination in the third trimester of pregnancy, complex pathologies in the health of the unborn child, which were not previously visualized, can be detected. The problem of developmental delay is in the first place in the list of these problems, since it is during this period – the period of active growth of the fetus – that this condition is perfectly noticeable. If any pathological changes are detected, doctors will prescribe another ultrasound 2 weeks after the one to make sure the diagnosis is made. It is also often required to conduct a second ultrasound in the third trimester if the centimeters of the standing uterus do not correspond to the norm. However, in this case, a simple physiological feature of a particular female body or a special position of the fetus at the time of examination is often revealed.

After the 30th week of pregnancy, developmental delay, for the most part, occurs according to an asymmetric developmental scenario, when, for example, the diameter of the abdomen does not correspond to the norms of development in a given period, but the diameter of the head does. Such delays occur due to impaired blood flow and are difficult to correct.

A feature of the third trimester is the ability of doctors to diagnose heart defects in a child, since the heart becomes well visualized, and its beat frequency is set in certain ranges.

Pros and Cons of Third Trimester Ultrasound

Despite the fact that in the medical environment, ultrasound in the third trimester of pregnancy is very welcome, many women are still afraid to do it because of the imaginary harm to the child. At the same time, doctors argue the need for ultrasound at such a period by the fact that this is the only way to determine the presentation and entanglement of the fetus with the umbilical cord, the weight of the unborn child at the end of pregnancy, which in the future will absolutely demonstrate how childbirth should be carried out. Also, the importance of ultrasound is to demonstrate infectious processes, developmental pathologies and the general condition of the unborn baby. The radiation during the ultrasound is scanty and does not affect the health of either the mother or the child at all. Thus, there is a real opportunity to make sure that your baby is completely safe, his health and that the birth will be easy and without complications.