Ultrasound signs of abnormalities in the first trimester of pregnancy

Non-viable pregnancy

A non-developing pregnancy often occurs with anembryony and is quite common. During an ultrasound examination, the fertilized egg is smaller in size than expected for the expected gestational age, and the embryo is not visualized.

If clinically early pregnancy is normal, and the ultrasound scan only reveals an enlarged uterus, anembryony may be suspected: the examination should be repeated in 7 days. If the pregnancy is normal, the fertilized egg will grow, the embryo will be clearly visualized, and its heartbeat will be recorded.

Non-viable pregnancy (spontaneous abortion)

After the death of the fetus or embryo, the patient may still feel pregnant for some time. Anamnestic data may reveal bleeding and abdominal pain of a spastic nature. The uterus may be of normal size, may be reduced, or may even be enlarged if there is a hematoma in the uterine cavity. The embryo may be visualized, but there will be no heartbeat. If the examination is performed before 8 weeks of pregnancy, a repeat examination must be performed after 7 days. After the 8th week, with a normal pregnancy, the fetus's vital activity must be determined without fail.

After the 8th week of pregnancy, the fetal heartbeat should always be detected.

Uterus after miscarriage

If the patient had a miscarriage shortly before the examination after a missed period (the fetus is sometimes detected during bleeding), then the uterus will be enlarged in accordance with the gestational age during the ultrasound examination. The uterine cavity will be empty.

Incomplete abortion

The patient's medical history shows a delay in menstruation followed by bleeding, and the patient can see the fetus. The uterus will be enlarged in accordance with the gestational age. The uterus may be empty, and the uterine cavity will not be enlarged. In case of incomplete abortion, the uterus will be smaller in size than expected for the gestational age, and a deformed ovum or amorphous masses of varying size, shape, and echogenicity may be detected in the cavity. These may be pieces of placenta, blood clots. Signs of fetal vital activity will not be determined.

After a miscarriage, it is quite difficult to determine the presence of a previous pregnancy. The diagnosis is established only in the presence of precise signs of a previous pregnancy, such as a yolk sac, a fertilized egg, a dead embryo. Thickening of the endometrium is an insufficient sign for diagnosing a past abortion, and it is also necessary to exclude a hydatidiform mole.

Be careful: the gestational age determined by the patient herself may not always be accurate.

Enlarged uterus

The most common causes of uterine enlargement are:

• hydatidiform mole;
• choriocarcinoma;
• uterine bleeding due to spontaneous abortion:
• uterine fibroids (fibroids).

Hydatidiform mole. Clinical findings are non-specific. The echographic picture is always altered, revealing an enlarged uterus with a fairly uniform distribution of echo signals, a spotty echostructure, creating a "snowstorm" effect. It may be difficult to distinguish a hydatidiform mole from hyperechoic blood in the uterine cavity, but blood is usually more heterogeneous in structure and has less echogenicity than a hydatidiform mole, in which cystic structures (bubbles) are determined. In older patients, a large myoma can simulate a hydatidiform mole, but in a hydatidiform mole, more pronounced dorsal enhancement and areas of central necrosis will be determined. It is very important to remember that the fetus may still be present, while only part of the placenta will be affected. An embryo in combination with a hydatidiform mole has a very high risk of developing chromosomal aberrations.

Choriocarcinoma may be indistinguishable from hydatidiform mole on sonography. This pathology may be suspected in the presence of a much larger enlargement of the uterus than expected for the gestational age. and sonography reveals more pronounced areas of hemorrhage and necrosis than in hydatidiform mole, which is characterized by the presence of monomorphic cystic structures. The echostructure of choriocarcinoma is heterogeneous, with alternating solid and cystic components: in hydatidiform mole, the echostructure is more homogeneous, characterized by the "snowstorm" effect. Less often, metastasis of choriocarcinoma is determined: chest X-ray is necessary to exclude metastases.

Uterine bleeding as a result of medical or spontaneous abortion. This is mainly a clinical diagnosis established in the presence of bleeding in the early stages of pregnancy: ultrasound can determine varying amounts of blood in the uterus, stratifying the chorioamniotic and decidual membranes (the membranes that are part of the endometrium), visualized as a virtually anechoic zone. The blood can be completely anechoic, or it can be hyperechoic. Usually, the blood is represented by a heterogeneous structure. It is very important to determine the presence of signs of fetal vital activity, since this will determine the tactics of managing this patient. If there are any doubts, it is necessary to repeat the study at an interval of L or 2 weeks to determine the progression of pregnancy.

If there are any doubts, the study is repeated after 1-2 weeks.

Enlarged, lumpy uterus. In the first trimester of pregnancy, an enlarged, lumpy uterus may be present in the presence of a myoma. Determine the size and position of the myomatous nodes in order to predict possible complications during labor. It is necessary to repeat the examination in the presence of a myoma at 32-36 weeks of pregnancy. The central zones of the myoma may become necrotic, with a heterogeneous or anechoic structure in the center being determined. This is of no significant clinical significance. Myoma can be simulated by thickening of the myometrium during contraction of the uterine muscles. In order to differentiate these conditions, the examination can be repeated after 20-30 minutes and it can be determined whether the zone of thickening of the myometrium changes. Contractions of the uterus are normal and change the internal contour of the uterus.