A molar pregnancy is one condition in a range of problems known as trophoblastic disease, where a pregnancy doesn’t grow as it should. It’s sometimes called a hydatiform mole.
There are two different types of molar pregnancy, which differ in how they form and how they need to be treated.
In a normal pregnancy, genetic material from the mother and father combines to form new life. In a molar pregnancy, this process goes wrong. In a complete molar pregnancy, the maternal chromosomes are lost, either at conception or while the egg was forming in the ovary, and only genetic material from the father develops in the cells. In a partial molar pregnancy, there is a set of maternal chromosomes but also two sets of chromosomes from the father (ie, double the normal paternal genetic material).
The genotype is typically 46,XX (diploid) due to subsequent mitosis of the fertilizing sperm, but can also be 46,XY (diploid). In contrast, a partial mole occurs when an egg is fertilized by two sperm or by one sperm which reduplicates itself yielding the genotypes of 69,XXY (triploid) or 92,XXXY (quadraploid).
Complete molar pregnancies develop as a mass of rapidly growing cells but without a foetus – it cannot therefore develop into a baby.
In a partial molar pregnancy, a foetus may start to develop but because of the imbalance in genetic material, it’s always abnormal and can’t survive beyond the first three months of pregnancy.
A molar pregnancy is often harmless, but if untreated can keep on growing and become invasive, spreading to the organs around it, or even further afield to the lungs, liver or brain. Very rarely, in two to three per cent of cases, it may become malignant. These cancerous types of trophoblastic disease are called choriocarcinoma and placental site trophoblast tumours.
As the mole grows faster than a normal foetus would, the abdomen may become larger more quickly than would be expected for the dates of the pregnancy. The woman may experience abdominal pain, and also severe nausea and vomiting (hyperemesis).
Bleeding from the vagina is another common warning sign that things are not as they should be. Symptoms similar to pre-eclampsia – high blood pressure, protein in the urine, swelling of the feet and legs – may also occur in the first trimester or early in the second.
Most molar pregnancies are diagnosed at the first ultrasound scan, which shows a mass of cells without the presence of a foetus in a complete molar pregnancy or an abnormal non-viable foetus and placenta in a partial mole.
A woman with a hydatidiform mole often feels pregnant and has symptoms such as morning sickness, probably because the cells of the molar pregnancy produce the pregnancy hormone hCG (human chorionic gonadotrophin). This is also the hormone that is used in a pregnancy test, so she may have a positive result. Some women have no pregnancy symptoms (as with many normal pregnancies). — but most molar pregnancies cause specific signs and symptoms, including:
*Dark brown to bright red vaginal bleeding during the first trimester
*Severe nausea and vomiting
*Vaginal passage of grape-like cysts
*Rarely, pelvic pressure or pain
If you experience any signs or symptoms of a molar pregnancy, consult your health care provider. He or she may detect other signs of a molar pregnancy, such as:
*Rapid uterine growth — the uterus is too large for the stage of pregnancy
*Preeclampsia — a condition that causes high blood pressure and protein in the urine after 20 weeks of pregnancy
*Overactive thyroid (hyperthyroidism)
A molar pregnancy is caused by an abnormally fertilized egg. Human cells normally contain 23 pairs of chromosomes. One chromosome in each pair comes from the father, the other from the mother. In a complete molar pregnancy, all of the fertilized egg’s chromosomes come from the father. Shortly after fertilization, the chromosomes from the mother’s egg are lost or inactivated and the father’s chromosomes are duplicated. The egg may have had an inactive nucleus or no nucleus.
In a partial or incomplete molar pregnancy, the mother’s chromosomes remain but the father provides two sets of chromosomes. As a result, the embryo has 69 chromosomes, instead of 46. This can happen when the father’s chromosomes are duplicated or if two sperm fertilize a single egg.
It remains unclear why a hydatidiform mole develops. However, there are a number of possible reasons, including defects in the egg, maternal nutritional deficiencies and uterine abnormalities. Women under 20 or over 40 are at higher risk.
Having a diet that’s low in protein, folic acid and carotene also increases the risk of a molar pregnancy. The number of times a women has been pregnant, however, doesn’t influence her risk.
Up to an estimated 1 in every 1,000 pregnancies is molar. Various factors are associated with molar pregnancy, including:
*Maternal age. A molar pregnancy is more likely for a woman older than age 35 or younger than age 20.
*Previous molar pregnancy. If you’ve had one molar pregnancy, you’re more likely to have another. The risk of a repeat molar pregnancy is 1 in 100.
*Some ethnic groups. Women of Southeast Asian descent appear to have a higher risk of molar pregnancy.
Molar pregnancies usually present with painless vaginal bleeding in the fourth to fifth month of pregnancy. The uterus may be larger than expected, or the ovaries may be enlarged. There may also be more vomiting than would be expected (hyperemesis). Sometimes there is an increase in blood pressure along with protein in the urine. Blood tests will show very high levels of human chorionic gonadotropin (hCG).
The diagnosis is strongly suggested by ultrasound (sonogram), but definitive diagnosis requires histopathological examination. On ultrasound, the mole resembles a bunch of grapes (“cluster of grapes” or “honeycombed uterus” or “snow-storm”). There is increased trophoblast proliferation and enlarging of the chorionic villi. Angiogenesis in the trophoblasts is impaired as well.
Sometimes symptoms of hyperthyroidism are seen, due to the extremely high levels of hCG, which can mimic the normal Thyroid-stimulating hormone (TSH).
Once it has been established that a woman is carrying a hydatidiform mole rather than a healthy foetus, suction evacuation is used to remove the pregnancy from the womb. This is curative in about four out of five molar pregnancies.
It’s then important to monitor the woman’s progress and repeatedly measure human chorionic gonadotropin (hCG) to be sure that everything settles back down to a normal, non-pregnancy level.
About 15 per cent of women who have had a complete molar pregnancy and 0.5 per cent of those with a partial molar pregnancy will require additional treatment, either because hCG levels hit a plateau or start to rise again, or because of persistent heavy vaginal bleeding.
Further treatment may involve the use of chemotherapy (usually methotrexate combined with folinic acid), especially if there’s any concern about invasive or malignant disease.
After a molar pregnancy has been removed, molar tissue may remain and continue to grow. This is called persistent gestational trophoblastic disease (GTD). It occurs in about 10 percent of women after a molar pregnancy — usually after a complete mole rather than a partial mole. One sign of persistent GTD is an HCG level that remains high after the molar pregnancy has been removed. In some cases, an invasive mole penetrates deep into the middle layer of the uterine wall, which causes vaginal bleeding. Persistent GTD can nearly always be successfully treated, most often with chemotherapy. Another treatment option is removal of the uterus (hysterectomy).
Rarely, a cancerous form of GTD known as choriocarcinoma develops and spreads to other organs. Choriocarcinoma is usually successfully treated with multiple cancer drugs.
More than 80% of hydatidiform moles are benign. The outcome after treatment is usually excellent. Close follow-up is essential. Highly effective means of contraception are recommended to avoid pregnancy for at least 6 to 12 months.
In 10 to 15% of cases, hydatidiform moles may develop into invasive moles. This condition is named persistent trophoblastic disease (PTD). The moles may intrude so far into the uterine wall that hemorrhage or other complications develop. It is for this reason that a post-operative full abdominal and chest x-ray will often be requested.
In 2 to 3% of cases, hydatidiform moles may develop into choriocarcinoma, which is a malignant, rapidly-growing, and metastatic (spreading) form of cancer. Despite these factors which normally indicate a poor prognosis, the rate of cure after treatment with chemotherapy is high.
Over 90% of women with malignant, non-spreading cancer are able to survive and retain their ability to conceive and bear children. In those with metastatic (spreading) cancer, remission remains at 75 to 85%, although their childbearing ability is usually lost.
Following successful treatment, most women can have children if they wish. However, it’s strongly recommended that a woman who has had a molar pregnancy doesn’t become pregnant again for 12 months. Although the likelihood is small, there’s a real risk of malignant disease developing and the increase in pregnancy hormones this would cause can’t be distinguished from those of a real pregnancy. Consequently, good contraception is required, as is regular monitoring by a hospital specialist.
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose
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