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The mystery of choriocarcinoma: Why is this abnormal pregnancy so rare?
Chorionic uteri, or vesicular fetus, is an abnormal pregnancy condition that occurs when a nonviable fertilized egg implants in the uterus. This condition falls under the category of gestational trophoblastic diseases. In the case of vesicular pregnancies, there is a growing mass in the uterus, characterized by edematous villous villi and shaped like a bunch of grapes. The occurrence of chorionic disease is related to the lack of maternal nucleus in the fertilized egg. Because of this condition, the result of conception may not contain embryonic tissue. This abnormal pregnancy is divided into two categories: partially blister fetuses and completely blister fetuses, where "blister" simply means an accumulation of growing tissue.
Most cases of complete blister fetuses are caused by the combination of one sperm or two sperm with an egg that has lost its DNA.
In the United States, the incidence of blister pregnancies is about 1 in 1,000 pregnancies, while in some countries in Asia, such as Indonesia, the incidence is as high as about 1 in 100 pregnancies. This makes vesicular pregnancies a relatively rare pregnancy complication.
Symptoms and signs
Blistered fetuses usually present with painless vaginal bleeding during the fourth to fifth trimester of pregnancy. The uterus may be larger than expected, or the ovaries may be enlarged. Additionally, patients may experience more vomiting than expected (hyperemesis gravidarum). This is sometimes accompanied by an increase in blood pressure and the presence of protein in the urine. Blood tests will show very high chorionic gonadotropin (hCG) levels.
Cause
The cause of this disease is not fully understood. Potential risk factors may include egg defects, abnormalities within the uterus, or nutritional deficiencies. Women under 20 or over 40 are at higher risk. Other risk factors include a diet low in protein, folate and carotene.
The DNA composition and gene expression patterns of germ cells result in different types of blister fetuses having different demands for reproductive resources.
Diagnosis
Diagnosis is usually strongly suggested by ultrasound (sound examination), but confirmation requires histopathological examination. In ultrasound, blister fetuses appear to have characteristics that resemble a "bunch of grapes", a "honeycomb uterus" or a "snowstorm". The trophoblast of the placenta proliferates, the villous villi enlarge, and angiogenesis in the trophoblast is impaired. Symptoms of hyperthyroidism sometimes occur because extremely high levels of hCG mimic the effects of thyroid stimulating hormone.
Treatment Plan
After a vesicular fetus is discovered, the uterus should be suctioned out or surgically curettaged promptly to reduce the risk of developing choriocarcinoma. Patients need to be followed up until hCG levels drop to undetectable levels. Invasive or metastatic cystitis (cancer) may require chemotherapy and usually responds well to methotrexate. Because they contain paternal antigens, the response to treatment is almost 100%. Patients are advised not to become pregnant again within six months after hCG levels become normal.
Prognosis
More than 80% of blister pregnancies are benign, and the results after treatment are usually good. Close follow-up is crucial to ensure treatment is successful. Still, women who have had a partially or completely bleb-filled pregnancy are at slightly increased risk in future pregnancies.
In some cases, vesicular pregnancies can develop into invasive vesicular pregnancies, a condition called persistent trophoblastic disease.
With the development of medicine, the understanding and treatment of blister fetuses are also constantly improving. However, the rarity of this abnormal pregnancy still makes people think about how we should better face possible risks and challenges during pregnancy in the future.
