Placental ultrasound

The condition of the fetus, its growth and development largely depend on the condition of the placenta; the condition of the placenta can be accurately and accurately assessed by echography. The exact location of the placenta is determined in relation to the fetus and to the axis of the cervix. The structure of the placenta and the uteroplacental connection can also be assessed.

Examination of the placenta is a very important part of every obstetric ultrasound examination.

Localized thickening of the myometrium during uterine contraction may simulate the placenta or the formation of the uterine wall.

Scanning technique

The patient should have a full but not over-distended bladder so that the lower uterine segment and vagina are clearly visible. Ask the patient to drink 3 or 4 glasses of water before the examination.

To examine the placenta, multiple longitudinal and transverse sections must be made. Oblique sections may also be necessary.

Normal placenta

At 16 weeks of pregnancy, the placenta occupies half of the inner surface of the uterus. At 36-40 weeks, the placenta occupies from 1/4 to 1/3 of the area of the inner surface of the uterus.

Uterine contraction may simulate placenta or a mass in the uterine wall. Repeat the examination after 5 minutes, but keep in mind that contraction may last longer. If in doubt, wait a little longer.

Accurate determination of the location of the placenta is very important for patients with vaginal bleeding or signs of fetal distress, especially in late pregnancy.

Overdistension of the bladder can sometimes create a false echographic picture of placenta previa. Ask the patient to partially empty the bladder and repeat the examination.

Placenta location

The placenta is easily visualized starting from the 14th week of pregnancy. To examine the placenta located on the posterior wall, it is necessary to make oblique cuts.

The location of the placenta is assessed in relation to the uterine wall and the axis of the cervical canal. The location of the placenta may be as follows: along the midline, on the right side wall, on the left side wall. The placenta may also be located on the anterior wall, on the anterior wall extending to the fundus. in the fundus area, on the posterior wall, on the posterior wall extending to the fundus.

Placenta previa

Visualization of the cervical canal is essential when placenta previa is suspected. The cervical canal is visualized as an echogenic line surrounded by two hypo- or anechoic rims, or it may be entirely hypoechoic. The cervix and lower uterine segment will be visualized differently depending on the degree of bladder filling. With a full bladder, the cervix appears elongated; lateral shadows from the fetal head, bladder, or pelvic bones may obscure some details. With less bladder filling, the cervix changes its orientation to a more vertical position and becomes perpendicular to the scanning plane. The cervix is more difficult to visualize with an empty bladder, but under these conditions it is less displaced, and the relationship of the placenta to the cervical canal is more clearly defined.

The diagnosis of placenta previa, established during examination with a full bladder, should be confirmed by examination after its partial emptying.

Placenta location

1. If the placenta completely covers the internal cervical os, then this is central placenta previa.
2. If the edge of the placenta covers the internal cervical os, there is a marginal placenta previa (in this case, the internal cervical os is still completely covered by placental tissue).
3. If the lower edge of the placenta is close to the internal cervical os, there is a low placental insertion. This diagnosis is difficult to establish accurately, since only part of the cervical os is covered by the placenta.

The location of the placenta may change during pregnancy. If the examination is performed with a full bladder, the examination should be repeated with a partially empty bladder.

Placenta previa may be detected early in pregnancy and not detected at the end. However, central placenta previa is diagnosed at any stage of pregnancy, marginal placenta previa - after 30 weeks, and after that, no significant changes are noted. If there is no bleeding in the second trimester of pregnancy, the second standard ultrasound examination of the placenta can be postponed until 36 weeks of pregnancy to confirm the diagnosis of placenta previa. If there is any doubt, the examination should be repeated before 38 weeks of pregnancy or immediately before delivery.

Normal echostructure of the placenta

The placenta may be homogeneous or have isoechoic or hyperechoic foci along the basal layer. In the last stages of pregnancy, echogenic septa may be detected throughout the entire thickness of the placenta.

Anechoic areas just below the chorionic plate or within the placenta are often found as a result of thrombosis and subsequent fibrin accumulation. If they are not extensive, they may be considered normal.

Intraplacental anechoic areas may be caused by blood flow visible in dilated veins. If they involve only a small part of the placenta, they are of no clinical significance.

Under the basal layer of the placenta, retroplacental hypoechoic channels can be seen along the uterine wall as a result of venous outflow. These should not be confused with retroplacental hematoma.

Placental pathology

A hydatidiform mole can be easily diagnosed by its characteristic "snow storm" sonographic appearance. It should be noted that the fetus may still be alive if the process affects only part of the placenta.

Enlargement (thickening) of the placenta

Measuring the thickness of the placenta is too imprecise to significantly influence the diagnosis process. Any assessment is quite subjective.

1. Thickening of the placenta occurs in cases of Rhesus conflict or fetal hydrops.
2. Diffuse thickening of the placenta can be observed in mild forms of diabetes mellitus in the mother.
3. The placenta may thicken if the mother had an infectious disease during pregnancy.
4. The placenta may be thickened in placental abruption.

[ 1 ], [ 2 ], [ 3 ], [ 4 ]

Thinning of the placenta

1. The placenta is usually thin if the mother has insulin-dependent diabetes.
2. The placenta may be thinner! Ia, if the mother has preeclampsia or intrauterine growth retardation of the fetus.

Placental abruption

Echography is not a very sensitive method for diagnosing placental abruption. Detachment is characterized by the presence of hypo- or anechoic areas under the placenta or raising the edge of the placenta. Blood can sometimes dissect the placenta.

The hematoma may appear hyperechoic, and sometimes its echogenicity is comparable to that of a normal placenta. In this case, the only sign of the hematoma may be a local thickening of the placenta, but the placenta may appear completely unchanged.

Ultrasound is not a very accurate method for diagnosing placental abruption. Clinical examination is still extremely important.