Ultrasound during pregnancy

Ultrasound diagnostics in obstetrics has been used for about 30 years. Although it is considered that ultrasound examination is practically harmless, nevertheless, studies are still being conducted to confirm this position. Echography is the most important tool for examining pregnant women and can be used for clinical indications at any stage of pregnancy.

Is a normal pregnancy an indication for an ultrasound examination?

This issue is still being debated and research is ongoing. However, there are two periods during physiological pregnancy when ultrasound is most useful and provides the most information.

These periods are:

1. From 18 to 22 weeks of pregnancy from the first day of the last menstrual period.
2. From 32 to 36 weeks of pregnancy from the first day of the last menstrual period.

The most informative period of time for conducting the first study (weeks)

1	2	3	4	5	6	7	8
9	10	11	12	13	14	15	16
17	18	19	20	21	22	23	24

The most informative time period for conducting the second study (weeks)

25	26	27	28	29	30	31
32	33	34	35	36	37	38
39	40

Why is an ultrasound examination performed during a physiological pregnancy?

Many doctors believe that ultrasound is not necessary for a normal pregnancy. Other doctors recommend the test because many fetal malformations cannot be detected by clinical examination.

1. 90% of fetal malformations occur without a family history of similar pathology, and only a very small number of mothers have obvious risk factors.
2. Even if the pregnancy is clinically normal, there may be very significant fetal malformations.
3. Neither clinical examination nor family history is a sufficiently clear way to establish multiple pregnancy.
4. A significant number of pregnant women with a low-lying placenta (placenta previa) do not have any clinical signs of this pathology until bleeding begins during physical exertion. The situation can become quite critical, especially if the patient is far from the hospital.
5. Up to 50% of women who claim to know the exact gestational age are actually off by more than 2 weeks when comparing the ultrasound data. The 2-week period is extremely critical for the survival of the fetus if there are indications for early delivery due to antenatal complications.

When is an ultrasound examination indicated before 18 weeks of pregnancy?

The patient should undergo a thorough clinical examination if the pregnancy test is positive or if menstruation is absent. Ultrasound scanning may be helpful if there is clinical evidence of possible pathology of pregnancy or if there is doubt about the gestational age.

Why is an ultrasound examination performed in early pregnancy (up to 18 weeks)?

Ultrasound examination in early pregnancy is performed:

1. To confirm the presence of pregnancy.
2. To accurately determine the gestational age.
3. To clarify the location of the fertilized egg (in the uterine cavity or ectopic).
4. To detect multiple pregnancies.
5. To exclude hydatidiform mole.
6. To exclude false pregnancy in the presence of formations in the pelvis or hormonally active ovarian tumors.
7. To diagnose fibroids or ovarian growths that could interfere with the normal course of labor.

Umbilical cord and umbilical vessels

The umbilical cord is determined already in the first trimester of pregnancy as a strand from the basal plate of the chorion to the embryo. Longitudinal and transverse sections allow visualization of one umbilical vein and two umbilical arteries. If only two vessels are visualized, this always means that there is no second artery, which is always accompanied by a high risk of intrauterine fetal death and combined fetal anomalies, which occur in 20% of cases.

There is also a high risk of intrauterine growth retardation in the fetus with only one umbilical artery. Fetal growth indicators should be recorded at each examination.

Multiple pregnancy

It is important to determine the position of each fetus and the number of placentas when detecting multiple pregnancies. The interamniotic septum can be visualized, which is usually easily determined in the first and second trimesters of pregnancy. If the fetuses are fraternal, this means the presence of dizygotic twins. It is necessary to measure each fetus to detect developmental pathology in each of them. It is also necessary to take into account the amount of amniotic fluid in each fetal egg.

Conclusion: ultrasound during pregnancy

Many physicians believe that there is no need for routine ultrasound examination at any stage of physiological pregnancy and that ultrasound examination is performed only in case of suspicion of pathology arising from clinical examination. Other physicians believe that two standard examinations are necessary for better antenatal diagnosis.

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Indications and timing of additional ultrasound examinations

Ultrasound cannot explain mild to moderate abdominal pain unless there is evidence of preeclampsia.

Indications for additional ultrasound examinations are:

1. Intrauterine growth retardation of the fetus.
2. Low placenta: repeat the examination at 38-39 weeks of pregnancy and, if necessary, immediately before delivery.
3. Fetal abnormality; repeat examination at 36 weeks.
4. Mismatch between uterine size and gestational age: repeat the examination at 36 weeks of pregnancy or earlier if the mismatch is significant.
5. Known or suspected fetal abnormality: repeat examination at 38-39 weeks.
6. Unexpected bleeding.
7. No fetal movement or other signs of intrauterine fetal death: repeat the test immediately, or if in doubt, after another week.

Preparing for an ultrasound examination during pregnancy

1. Patient preparation. The bladder should be full. Give the patient 4 or 5 glasses of fluid and perform the examination one hour later (the patient should not urinate). If necessary, fill the bladder through a urethral catheter with sterile saline: filling the bladder is stopped if the patient feels discomfort. Avoid catheterization whenever possible because of the risk of infection.
2. Patient position. The patient is usually examined in a relaxed position, lying on her back. If necessary, the patient can be turned during the examination. Apply the gel randomly to the lower abdomen: there is usually no need to apply the gel to the pubic hair, but if necessary, apply the gel to this area as well.
3. Sensor selection. Use a 3.5 MHz sensor. Use a 5 MHz sensor for thin women.
4. Adjusting the sensitivity level of the device. Place the sensor longitudinally on the projection of the filled bladder and set the sensitivity level necessary to obtain an optimal image.

What is important during the examination between 18 and 22 weeks of pregnancy?

This is the optimal period for:

1. Establishing the exact timing of pregnancy.
2. Diagnosis of multiple pregnancy.
3. Diagnosis of fetal pathology.
4. Determining the location of the placenta and identifying placenta previa.
5. Detection of fibroids or other pelvic growths that may interfere with pregnancy or childbirth.

What is important during the examination between 32 and 36 weeks of pregnancy?

This is the optimal period for:

1. Diagnosis of fetal growth retardation syndrome.
2. Detection of fetal pathology that was not detected during the first ultrasound examination.
3. Detection of placenta previa and determination of the position of the fetus.
4. Determining the exact location of the placenta.
5. Determination of the amount of amniotic fluid.
6. Exclusion of concomitant pathology, such as fibroids, ovarian tumors.

18-22 weeks of pregnancy

Ultrasound at these stages of pregnancy will help answer the following questions:

1. Is it a singleton or multiple pregnancy?
2. Does the actual gestational age correspond to that estimated by the clinical study?
3. Do the fetal development parameters correspond to normal values for this stage of pregnancy?
4. Is the fetal anatomy normal?
5. Is fetal activity normal?
6. Is the condition of the uterus normal?
7. Is the amount of amniotic fluid normal?
8. Where is the placenta located?

32-36 weeks of pregnancy

Ultrasound at these stages of pregnancy will help answer the following questions:

1. Are fetal developmental signs normal?
2. Is the fetus in normal condition? Are there any developmental abnormalities?
3. What is the position of the fetus (although this may change before birth)?
4. Where is the placenta located?
5. Is the amount of amniotic fluid normal?
6. Are there any concomitant diseases, such as fibroids, ovarian tumors, that may affect the course of pregnancy and childbirth?

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Late pregnancy

If the patient has not previously undergone an ultrasound examination, an ultrasound scan during a late pregnancy examination will help answer the following questions:

1. Is it a singleton or multiple pregnancy?
2. Does the degree of maturity of the fetus correspond to the established gestational age?
3. What is the position of the fetus?
4. What is the location of the placenta? In particular, it is necessary to exclude the presence of placenta previa.
5. Is the amount of amniotic fluid normal?
6. Are there any fetal developmental abnormalities?
7. Are there any concomitant diseases, such as fibroids, ovarian tumors, that may affect the course of pregnancy and childbirth?

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Ultrasound before and after the procedure of bringing down the fetal head

It is often necessary to conduct a study immediately before the fetus turns from the breech to the cephalic position to be sure that the fetus has not already changed its position.

After the turning procedure, an ultrasound scan is necessary to ensure that the fetus's position has returned to normal.

Ultrasound examination in early pregnancy (up to 18 weeks)

If an ultrasound scan is indicated, it is preferable to wait until 18-22 weeks of pregnancy, as the information obtained during the examination at this time will be most accurate. However, there may be indications for an ultrasound scan at an earlier time, for example:

1. Vaginal bleeding.
2. The patient does not know the date of her last menstrual period or has other reasons to suspect a mismatch in timing.
3. Absence of signs of fetal vital activity when pregnancy is suspected.
4. History of pathology in previous pregnancy or childbirth or other obstetric or genetic diseases.
5. The presence of an intrauterine contraceptive device.
6. The presence of indications for termination of pregnancy.
7. The patient is particularly concerned about the well-being of this pregnancy.

Ultrasound examination in mid-pregnancy (28-32 weeks)

It is advisable to postpone the examination until 32-36 weeks of pregnancy, however, there may be clinical indications for an ultrasound examination at an earlier stage, for example:

1. Clinical problems with the position or size of the fetal head.
2. Clinical examination allows us to suspect pathology.
3. Previous ultrasound examinations showed some pathology or were of unsatisfactory quality.
4. The position of the placenta was not accurately determined or the placenta was located close to the internal cervical os on a previous ultrasound examination.
5. The uterus is too large for the estimated gestational age.
6. There is amniotic fluid leakage.
7. There is pain or bleeding.
8. The mother's condition is unsatisfactory.

Ultrasound examination during childbirth

Indications for ultrasound examination during childbirth are:

1. Unstable condition of the fetus.
2. Inability to clinically record fetal heartbeat.
3. Discrepancy between the gestational age and the size of the fetus.
4. Unusually heavy bleeding.
5. Weakness of labor or other complications of labor.

Ultrasound examination in the postpartum period

There is generally no clinical indication for routine ultrasound examination in the postpartum period, however there may be some clinical situations in which ultrasound examination may provide useful information.

In the early postpartum period:

1. Uterine bleeding.
2. Incomplete separation of the placenta or retention of placental tissue in the uterus.
3. A prolonged period of expulsion of the second fetus from twins.

6 weeks after birth:

1. Continued bleeding.
2. Constant pain.
3. Subinvolution of the uterus in the postpartum period.
4. Continued vaginal discharge.
5. Palpable formations in the pelvis.

When is ultrasound not recommended?

Ultrasound examination is not recommended in the first trimester of pregnancy unless there are clinical indications.

What is examined during a normal pregnancy?

Many doctors believe that the potential risk and high cost of performing ultrasound examinations on all women with normal pregnancies is not justified in terms of the benefits to patients.

The question of whether or not to conduct the study during a normal pregnancy is decided individually by the patient or the doctor each time. There are no uniform rules or recommendations on this issue.

Determining the sex of the fetus is not an indication for ultrasound examination, except in cases where there is a history of a sex-related hereditary disease.

Is ultrasound safe during pregnancy?

Yes, as far as we know. However, ultrasound examination should only be performed when clinically indicated.

Why is ultrasound not recommended during a pregnant woman's first visit to the doctor?

Some doctors recommend an ultrasound examination at a pregnant woman's first visit to the doctor, but this is not necessary in cases where there is no clinical indication. If there is an indication, the examination is preferably performed between 18 and 22 weeks of pregnancy, when the ultrasound provides the most important information.

There is no need to perform an ultrasound examination every month or at every visit to the doctor of a pregnant woman, except in cases where clinicians have reason to suspect the presence of pathology that requires dynamic monitoring.