Ultrasound signs of normal pregnancy

Normal pregnancy

The study of normal pregnancy should be carried out in a strictly defined order with the determination of the uterine condition and the anatomy of the fetus.

The following order of research is recommended:

1. Do an examination of the lower abdominal and pelvic organs of a pregnant woman.
2. Examine the fetus.
3. Remove the fetal head (including the skull and brain).
4. Remove the fetal spine.
5. Remove the fetal chest.
6. Bring out the abdomen of the fetus and the genitals.
7. Remove the fetal limb.

Normal pregnancy

The first ultrasound (ultrasound) should include an overview scan of the entire lower abdomen of a pregnant woman. The most common finding is the cyst of the yellow body, which, as a rule, is detected before the 12th week of pregnancy and has a diameter of up to 4 cm. Very large cysts can tear, and bleeding may occur. Testicular torsion can also be detected.

The adherents of the uterus, as well as the entire contents of the pelvis, should be carefully examined for any pathology, especially cicatricial changes, large ovarian cysts, large uterine fibroids, which can interfere with the normal development of pregnancy. In the case of pathology, it is necessary to evaluate the size of pathological structures and to conduct dynamic observation.

An ultrasound examination during pregnancy should involve the systematic establishment of anatomical relationships in the fetus.

With the exception of cases of anencephaly, the fetal organs can not be accurately evaluated until 17-18 weeks of gestation. After 30-35 weeks, the evaluation of the condition can be significantly hampered.

Examine the uterus for:

1. Definitions of the presence of fetus or multiple pregnancy.
2. Definitions of the placenta.
3. Definitions of the position of the fetus.
4. Determination of the amount of amniotic fluid.

The most important part of prenatal ultrasound diagnosis is the establishment of the fetal head condition.

Echographically, the fetal head begins to appear from the 8th week of pregnancy, but the study of intracranial anatomy is possible only after 12 weeks.

Technology

Scan the uterus to determine the fetus and the fetal head. Turn the sensor towards the head of the fetus and cut in the sagittal plane from the crown of the fetus to the base of the skull.

First, visualize the "middle echo", a linear structure from the forehead to the head of the head of the fetus. It is formed by the sickle of the large brain, the midline groove between the two hemispheres of the brain, and also the transparent septum. If the scan is performed at a level just below the crown, the median structure looks continuous and is formed by the sickle of the large brain. Below is defined an anechoic, rectangular zone anterior to the midline, which is the first rupture in the median echo. This is the cavity of the transparent septum. Immediately behind and below the septum are two relatively low echogenicity of the site - visual mounds. Between them two hyperechoic, parallel lines, caused by the lateral walls of the third ventricle (they are visualized only after 13 weeks of pregnancy) are identified.

At a slightly lower level, the median structures from the lateral ventricles disappear, but the anterior and posterior horns are still visualized.

Vascular plexuses are defined as echogenic structures filling the lateral ventricles. The anterior and posterior horns of the ventricles contain fluid, but not vascular plexuses.

When scanning 1-3 cm below (caudal), close to the upper part of the brain, try to visualize the structure in the form of a heart of low echogenicity with the apex directed toward the occipital region - the brain stem. Immediately anteriorly, the pulsation of the basilar artery will be determined and further ahead - pulsation of the vessels of the Willis circle.

Behind the brainstem, the cerebellum is determined, which is not always visualized. If the angle of inclination of the scanning plane changes, the bigbrain crescent will still be visualized.

Immediately below, the skull base is defined as an X-shaped structure. The anterior branches of this section are the wings of the sphenoid bone; posterior - the tops of the pyramids of the temporal bones.

The ventricles are measured above the BDP definition level. Look for a complete median structure from the cerebral crescent and two straight lines located close to the middle line in front and slightly diverging posteriorly. These are the veins of the brain, note at the same time the lateral walls of the lateral ventricles. Echogenic structures in the ventricles correspond to the vascular plexus.

To determine the size of the ventricles, calculate the ratio of the width of the ventricles to the width of the cerebral hemispheres at their widest part. Measure the ventricle from the center of the median structure to the lateral wall of the ventricles (cerebral veins). Measure the hemispheres of the brain from the median structure to the inner surface of the skull. The values of this ratio vary depending on the gestational age, but it is considered normal if it does not exceed 0.33. Higher values should be correlated with standard values for a given gestation age. Ventriculomegaly (usually with hydrocephalus) requires further in-depth study and dynamic observation. It is also necessary to observe the child in the early neonatal period.

In the anterior part of the fetal skull can visualize the orbit; lenses will be defined as bright hyperechogenic points located in the front. If you make the desired cut, you can visualize the face of the fetus in the sagittal or frontal planes. Movement of the mouth and tongue can be determined after 18 weeks of pregnancy.

If the position of the fetus allows, it is necessary to make a sagittal cut from the front for visualization of the frontal bone, upper and lower jaw and mouth.

Check that all facial structures are symmetrical and look normal, especially look carefully for cleavage of the upper lip and palate (this requires a certain skill).

Scan also the posterior sections of the skull and neck to identify a rare meningocele or occipital encephalocele. Scanning from the middle and laterally will help to identify the cystic hygroma. It is much easier to cross-scan the posterior parts of the skull and neck.)

The spine of the fetus

The spine of the fetus begins to be visualized from the 12th week of pregnancy. But it can be studied in detail, starting from the 15th week of pregnancy. In the second trimester of pregnancy (12-24 weeks), the body of the vertebrae has three separate centers of ossification: the central forms the body of the vertebra, and the two posterior form the arches. The arches are visualized in the form of two hyperechogenic lines.

Also, with transverse scanning, you can see three centers of ossification and normal skin over the spine, longitudinal sections along the entire length of the spine are necessary to identify a meningocele. Sections in the frontal plane can clearly define the relationship of the posterior centers of ossification.

Because of the presence of bends, it is difficult to obtain a full cut of the spine along its entire length after 20 weeks of pregnancy.

Fetal thorax

For examining the fetal chest, transverse sections are most useful, but longitudinal sections are also used. The cutoff level is determined by the pulsation of the fetal heart.

Heart of the fetus

Palpitation of the fetus is determined starting from the 8th week of pregnancy, but in detail the anatomy of the heart can be examined starting from 16-17 weeks of gestation. The heart of the fetus is almost perpendicular to the body of the fetus, since it practically lies on top of a relatively large liver. The transverse section of the thorax makes it possible to obtain an image of the heart along the long axis, while all four chambers of the heart are visualized. The right ventricle is located in front, close to the front wall of the chest, the left ventricle is deployed to the spine. The normal number of heartbeats is 120-180 in 1 min, but sometimes the reduction in the heart rate is determined.

Chambers of the heart are approximately the same size. The right ventricle has a practically rounded shape in the cut and a thick wall, the left ventricle is more oval in shape. Intraventricular valves should be visualized, and the interventricular septum should be complete. The flotation flap of the oval aperture in the left atrium should be visualized. (The heart of the fetus is visualized more clearly than in a newborn baby, since the fetal lungs are not filled with air and the fetal heart can be visualized in all projections.)

Fetal lungs

Lungs are visualized in the form of two homogeneous, average echogenicity of formations on both sides of the heart. They are not developed, until late in the third trimester, and at 35-36 weeks the echogenicity of the lungs becomes comparable with the echogenicity of the liver and spleen. When this happens, it is believed that they are ripe, but the maturity of the lung tissue can not be accurately assessed by echography.

Fetal aorta and inferior vena cava

The aorta in the fetus can be visualized on longitudinal sections: look for the aortic arch (with the main branches), the descending section of the aortic arch, the abdominal aorta, the bifurcation of the aorta into the iliac arteries. The lower hollow vein is visualized as a large vessel that flows into the right atrium just above the liver.

Diaphragm of the fetus

With longitudinal scanning, the diaphragm is defined as a relatively hypoechoic rim between the liver and lungs, moving during the act of breathing. Both hemispheres of the diaphragm must be identified. This can be difficult, because they are thin enough.

Fetal abdomen

Transverse sections of the abdomen are the most informative for visualization of the abdominal cavity organs.

Liver of the fetus

The liver fills the upper abdomen. The liver is homogeneous and practically up to the last weeks of pregnancy has a higher echogenicity than the lungs.

Umbilical vein

The umbilical vein is traced in the form of a small anehogenous tubular structure passing from the entrance to the abdomen along the middle line upward, through the parenchyma of the liver into the portal sinus. The umbilical vein is connected to the venous duct in the sinus, but the sine itself is not always visualized, since it is too small in comparison with the vein. If the position of the fetus allows, it is necessary to visualize the place of the umbilical vein entering the fetal abdomen.

Scan the abdomen of the fetus to determine the location of the cord in the fetus and determine the integrity of the abdominal wall.

Circumference of the fetal abdomen

To calculate the circumference or cross-sectional area of the abdomen in order to determine the body weight of the fetus, perform measurements on the cut, where the umbilical vein inside the portal sinus is visualized.

Spleen of the fetus

It is not always possible to visualize the spleen. When the spleen is visualized, it is located behind the stomach, has a semilunar form and a hypoechogenic internal structure.

Gall bladder of the fetus

The gallbladder is not always visualized, but if it is visualized it is defined as a pear-shaped structure located parallel to the umbilical vein in the right side of the abdomen. Because of the close location in this section, they can easily be confused. However, the umbilical vein pulsates and has a connection with other vessels. Vienna should be visualized first. The gallbladder is located to the right of the midline and ends at an angle of approximately 40 ° to the umbilical vein. It can be traced from the surface of the liver into the depth of the parenchyma.

Stomach fetus

The normal fetal stomach is represented by a liquid-containing structure in the left upper quadrant of the abdomen. It will vary in size and shape, depending on the amount of amniotic fluid swallowed by the fetus: the stomach is fairly active peristalsis in the norm. If the fetus is 20 weeks pregnant or later, the stomach is not visualized for 30 minutes of observation, it may be due to poor filling of the stomach, congenital absence of the stomach or gastric dystopia (for example, with congenital hernia of the esophagus of the diaphragm) or as a result of the lack of an esophagus and stomach in the presence of tracheoesophageal fistula).

The fetal bowel

Multiple bowel loops filled with fluid can be visualized in the 2nd and 3rd trimesters. The large intestine is usually visualized immediately below the stomach and mostly looks anechogenous and tubular. Hausters can be identified. The large intestine is usually better seen in the last weeks of pregnancy.

Kidney fetuses

Kidney can be defined starting from 12-14 weeks of pregnancy, but clearly visualized only with 16 weeks. On the transverse sections, the kidneys are defined as rounded hypoechoic structures on either side of the spine. Inside, hyperechoic renal pelvis is visualized; the capsule of the kidneys is also hyperechoic. The kidney pyramids are hypoechoic and look large. Normally, an insignificant dilatation (less than 5 mm) of the renal pelvis can be determined. It is important to determine the size of the kidneys by comparing the circumference of the kidney cut with the abdominal circumference.

The adrenal glands of the fetus

The adrenal glands begin to be visualized starting from the 30th week of pregnancy in the form of a relatively low echogenicity of the structure above the upper poles of the kidneys. They have an oval or triangular shape and can have dimensions equal to half the normal size of the kidney (this is much larger than that of newborns).

Bladder fetus

The bladder looks like a small cystic structure and is recognized in the pelvis from 14-15 weeks of gestation. If the bladder is not immediately visualized, repeat the test after 10-30 minutes. It is necessary to know that diuresis at 22 weeks gestation is only 2 ml / h, and at the end of pregnancy - already 26 ml / h.

Sexual fetal organs

The sex organs of a boy are easier to recognize than the sexual organs of a girl. The scrotum and penis are recognized starting from the 18th week of pregnancy, and the girl's external genitalia starting from the 22nd week. Eggs are visualized in the scrotum only in the third trimester, although in the presence of a small hydrocele (this is a variant of the norm), they can be detected earlier.

 

Recognizing the sex of the fetus with the help of echography is not of great importance, except for cases of sex-related hereditary pathology or multiple pregnancy, in which it is desirable to determine the zygosity and condition of the placenta.

The patient should not be informed about the future child's field until 28 weeks of pregnancy, even if this can be done earlier.

Fetal limbs

The limbs of the fetus are revealed starting from the 13th week of pregnancy. Each limb of the fetus must be visualized, and the position, length, and movement must be assessed. These studies can take quite a long time.

End sections of the hands and feet of the fetus are most easily discerned. Fingers are easier to visualize than wrist or metatarsal bones, which are ossified after birth. Fingers of hands and feet begin to be visualized starting from 16 weeks. The detection of anomalies of the hands and feet is quite difficult.

Long bones have a high echogenicity in comparison with other structures. The thigh is visualized more easily because of the restriction of movements; the shoulder is more difficult to visualize. The lower parts of the limbs (the peroneal and tibial, radial and ulnar bones) are visualized worst of all.

Fetal thigh

The easiest way to obtain a hip image is to scan the backbone along the spine to the sacrum: one of the hips will fall into the slice. Then you need to tilt the sensor slightly until a femur cross section is obtained along the entire length, and measurements can be taken.

When measuring the length of bones, you need to make sure that the bone is fully visualized: if the cut is not obtained over the entire length - the measurement values will be reduced in comparison with the true ones.