How is hydatidiform mole formed?

Molar pregnancy is very harmful to human health. Molar pregnancy is actually a tumor disease. Even if a curettage is performed, it can still become malignant. Therefore, regardless of whether there are any symptoms of physical discomfort, regular check-ups are necessary, and it is best not to have children within two years, otherwise molar pregnancy may still occur. If a molar pregnancy occurs, it must be treated in time.

How is hydatidiform mole formed?

Hydatidiform mole is also called hydatidiform mole. Hydatidiform mole is caused by the proliferation of trophoblastic cells of the placenta villi and interstitial edema after pregnancy, which forms blisters of varying sizes. The blisters are connected by pedicles to form a cluster, which is named after its shape like grapes. The exact cause of hydatidiform mole is still unclear. It is generally believed to be related to nutritional disorders (especially folic acid deficiency), infection (especially viral infection), genetics and immune dysfunction.

After pregnancy, the embryo produces many villi and implants them in the mother's uterus. The fetus relies on these large numbers of villi to exchange substances with the mother, obtain oxygen, nutrition and carry out metabolism. Under pathological conditions, due to edema of the villous interstitium, it contains a large amount of transparent serous fluid, which makes the volume extremely swollen, and each villus becomes an enlarged blister. The diameter is generally 0.2~0.5 cm, and some are even larger. These blisters are connected in clusters, resembling grapes, of different sizes, with thin and transparent blister walls, containing viscous fluid, and the blisters are filled with blood and blood clots.

What is the cause of hydatidiform mole?

There are two types of hydatidiform mole: complete hydatidiform mole and partial hydatidiform mole. A complete hydatidiform mole means that the fertilized egg does not develop into an embryo at all; a partial hydatidiform mole means that the fertilized egg cannot survive because of abnormal development. The occurrence of hydatidiform mole is closely related to nutritional status and socioeconomic factors.

Data show that people whose diets lack vitamin A, its precursor carotene and animal fat have a higher risk of developing the disease. Age is another major high-risk factor. The incidence rate is higher in older pregnant women, and the incidence rate in pregnant women under 20 years old is also significantly increased. A history of hydatidiform mole in a previous pregnancy is also a high-risk factor. A history of miscarriage and infertility can also predispose to hydatidiform mole.

The causes of the two types of hydatidiform moles are also different.

Complete hydatidiform mole:

During examination, the watery substance of a complete hydatidiform mole resembles clusters of grapes, ranging in size from a few millimeters to several centimeters in diameter. The watery substance fills the entire uterine cavity, and no fetus, its appendages, or traces of the fetus can be found during examination.

In a normal pregnancy, the fertilized egg receives 23 chromosomes from each parent. In most cases of complete hydatidiform mole, the fertilized egg does not receive chromosomes from the mother, but the chromosomes obtained from the father's sperm are copied, so the result is that the fertilized egg receives 2 sets of identical chromosomes from the father and no chromosomes from the mother. In this case, no embryo, amniotic sac or any normal placental tissue forms. Instead, the placental tissue forms a bunch of blisters that look like a bunch of grapes.

Partial hydatidiform mole:

During the examination, it was found that only some of the villi turned into blisters, which may be combined with embryonic or fetal tissue. Most fetuses were dead, and combined with full-term babies were extremely rare. It was often accompanied by developmental delay and multiple malformations. The incidence of partial hydatidiform mole is much lower than that of complete hydatidiform mole.

In most cases of partial mole, the fertilized egg receives a normal set of chromosomes from the mother but doubles the number from the father, resulting in a fertilized egg with 69 chromosomes instead of the normal 46. This can happen if a chromosome from a sperm is duplicated, or if two sperm fertilize the same egg. In this case, there is some normal placental tissue amidst the grape-like clusters of abnormal tissue. The fertilized egg does begin to develop into an embryo, so there may be a fetus, or some fetal tissue, and perhaps an amniotic sac. But even if a fetus is formed, in most cases it is not normal enough to survive.