What is Hydatidiform Mole?
A molar pregnancy, also known as a Hydatiform mole, falls under a group of illnesses known as gestational trophoblastic disease (GTD). These conditions come from the placenta—the organ that provides nourishment to the baby during pregnancy. What sets it apart is that the tumor originates from pregnancy tissue, not from the mother’s tissue. There are other types of gestational trophoblastic disease, such as gestational choriocarcinoma, which can be highly aggressive and invasive, and placental site trophoblastic tumors.
A hydatiform mole is further classified into two categories—a complete and a partial mole. This type of molar pregnancy is usually considered the non-aggressive form of gestational trophoblastic disease. However, it’s essential to know that even though hydatiform moles are generally harmless, they are in the early stages of becoming cancerous and have the potential to become harmful and invasive if not addressed promptly.
What Causes Hydatidiform Mole?
Hydatiform moles, as previously mentioned, come in two types: complete and partial. Complete moles are the most common and don’t contain any parts of an unborn baby, while partial moles may have traces of an unborn baby present.
What makes these moles different? Complete moles usually have double the typical set of genetic material (diploid), while partial moles have three times the typical set (triploid). It’s also common for complete moles to cause higher than normal levels of a hormone called human chorionic gonadotropin (hCG), a key indicator of this condition.
Here’s a bit more information on the genetic makeup: Complete moles are generally 46,XX (which means they have 46 chromosomes and two X sex chromosomes) 90% of the time, and 46,XY (46 chromosomes with one X and one Y sex chromosome) 10% of the time. They form when an egg that has had its nucleus removed or ‘enucleated’ is fertilized by either two sperms or by one sperm that then duplicates.
Partial moles, on the other hand, are generally triploid 90% of the time, with their genetic make-up typically being 69,XXX or 69,XXY. This occurs when a normal sperm fertilizes an egg that duplicates, or when two sperms fertilize a single egg.
In partial moles, both the mother’s and the father’s genetic material or DNA is expressed.
Risk Factors and Frequency for Hydatidiform Mole
Hydatiform moles, a pregnancy complication, are pretty rare, especially in North America and Europe where it impacts between 60 to 120 out of every 100,000 pregnancies. However, its occurrence is a bit higher in other parts of the world. The chances of having a molar pregnancy can increase due to several risk factors:
- Age of the mother – being over 35 or in the early teenage years can significantly raise the risk
- A history of molar pregnancy – this increases the risk by 1 to 2% for future pregnancies
- Having had previous miscarriages or difficulties getting pregnant
- Diet – particularly, diets which are deficient in carotene (which is needed to make vitamin A) and animal fats
- Smoking
Signs and Symptoms of Hydatidiform Mole
A hydatiform mole is a rare condition in pregnancy. It occurs when a mass or “mole” forms in the uterus instead of a normal pregnancy. The symptoms of a hydatiform mole differ between a complete mole and a partial mole. Usually, partial moles are discovered after a spontaneous abortion when looking at the fetal tissue under a microscope.
Since ultrasound technology has advanced, doctors are now able to identify complete molar pregnancies earlier, often in the first three months of pregnancy. The most common symptom, experienced by around 84% of patients in one study, is vaginal bleeding in the early stages of pregnancy. This happens when the molar tissue separates from the uterine lining, causing bleeding. The blood is described as having a “prune juice” appearance due to the oxidation and liquefaction of blood in the uterine cavity. Patients may also experience severe nausea and vomiting, also known as hyperemesis, due to high levels of the hCG hormone in the bloodstream. Some women report passing vaginal tissue that looks like grape-like clusters.
Later signs of a complete molar pregnancy, usually appearing 14 to 16 weeks into the pregnancy, include symptoms of hyperthyroidism such as rapid heart rate and tremors. This is also caused by high levels of hCG. Other possible complications are pre-eclampsia, a condition characterized by high blood pressure and protein in the urine, and/or organ malfunction usually occurring after 34 weeks of pregnancy. Should a pregnant woman less than 20 weeks into her pregnancy show signs of pre-eclampsia, doctors may suspect a complete molar pregnancy. In extreme cases, patients may experience severe breathing difficulties due to a possible blood clot in the lungs from the molar tissue.
Partial hydatiform moles usually present less dramatically than complete moles. Symptoms resemble those of a threatened or spontaneous abortion, including vaginal bleeding. As partial hydatiform moles contain fetal tissue, these patients may have detectable fetal heart tones on Doppler ultrasound.
Physical examination can often reveal a discrepancy in uterine size. In over half the cases, the uterine size doesn’t match the expected gestational age of the pregnancy. Typically, in a complete mole, the uterus is larger than expected, while in partial moles the uterus might be smaller than expected.
Testing for Hydatidiform Mole
If a pregnant woman experiences vaginal bleeding, the standard procedure is to measure the level of a hormone called hCG in her blood and also check her blood type. In a pregnancy abnormality called a hydatiform mole, the levels of hCG are notably higher than they would be in a normal pregnancy or in an ectopic pregnancy. A “complete mole” is associated with extremely high hCG levels, often more than 100,000, while a “partial mole” could have hCG levels that are normal for the pregnancy stage or even lower than expected. Knowing the blood type is important as vaginal bleeding is common in patients with complete or partial hydatiform moles. This helps decide if it’s necessary to give these patients an anti-D immunoglobulin treatment if they are Rh(D) negative.
Other laboratory tests that might be done include a complete blood count to check for anemia and low platelet count, a comprehensive metabolic panel to check for electrolyte imbalances and kidney problems, tests for thyroid function if hyperthyroidism is suspected, liver function tests and urine tests if there’s a suspicion of pre-eclampsia (a pregnancy complication characterized by high blood pressure), and a coagulation profile to check for a condition called disseminated intravascular coagulation in severe cases.
In cases of suspected hydatiform mole, the best method of imaging is a pelvic ultrasound. This can reveal a mass in the uterus with many small, fluid-filled spaces which are usually referred to as a “snowstorm” pattern. This is seen in complete moles, where there’s no embryo or fetus and no amniotic fluid. In partial moles, there’s often a fetus which might be alive, the presence of amniotic fluid, and the placenta appears enlarged with cystic spaces, often described as a “Swiss cheese” appearance. It’s important to note that a significant percentage of partial moles are initially diagnosed as a missed or incomplete abortion.
When a molar pregnancy is diagnosed, normally a CT scan and PET scan will be performed to determine the extent of the disease. If the patient had initial symptoms of breathing distress or increased rate of breathing, a chest x-ray should also be carried out to check for a condition called pulmonary edema.
Treatment Options for Hydatidiform Mole
In the emergency room, the first focus is on stabilizing the patient. If a patient has trouble breathing or shows signs of fluid build-up in the lungs, they may need to receive additional oxygen. This can be accomplished through non-invasive positive pressure ventilation (a type of breathing support) or, in more severe cases, through a mechanical ventilator.
If a patient presents symptoms of late-stage pre-eclampsia, a condition called eclampsia, which includes seizures, doctors will begin appropriate treatment. This usually involves medications such as benzodiazepines to control the seizures and magnesium sulfate to prevent further seizures. If a patient shows signs of pre-eclampsia, which can include high blood pressure, medication will be administered to bring blood pressure levels down promptly. This often involves drugs like hydralazine and labetalol.
If the patient experiences signs and symptoms of hyperthyroidism, a condition where the thyroid is overactive, the healthcare provider should start the correct treatment. This often includes beta-blockers, a type of medication that can help control symptoms, and constant monitoring for extreme hyperthyroidism, also known as a thyroid storm.
When a patient has severe anemia, or a lack of red blood cells, a blood transfusion might be necessary. As mentioned earlier, if a patient has a particular blood type, called Rh(D) negative, a medication called anti-D immunoglobulin should be given.
Once the patient’s condition has been stabilized, a consultation with a specialist in pregnancy and childbirth (obstetrician) will likely be needed. This is usually because a procedure known as dilation and curettage (D and C) may need to be carried out. This procedure helps to diagnose and treat various conditions by removing tissue from inside your uterus. Older patients, usually over 40 years old, or those who do not want more children, may have a hysterectomy. This is a surgery to remove the uterus. However, a hysterectomy does not fully remove the risk of the disease spreading to other areas of the body.
Following a molar pregnancy, a particular event where a non-viable fertilized egg implants into the uterus, your doctor should monitor your hCG levels. If these levels do not decrease, this could be a sign of persistent disease that has spread or become invasive. In these cases, chemotherapy might be needed, and a consultation with a gynecological oncologist, a doctor who specializes in diagnosing and treating cancers that are located on a woman’s reproductive organs, is often necessary.
What else can Hydatidiform Mole be?
Here are some conditions related to pregnancies that can have various impacts and complications:
- Androgenetic/biparental mosaic conceptions: it’s a rare type of pregnancy anomaly
- Abnormal villous morphology: unusual formation of structures inside the placenta
- Early abortus with trophoblastic hyperplasia: early termination of pregnancy with unusual growth of the cellular lining of the uterus
- Hydropic abortus: a condition when a pregnancy ends, and the placental tissue becomes swollen with fluid
- Hyperemesis gravidarum: severe nausea and vomiting during pregnancy
- Hypertension: high blood pressure
- Hyperthyroidism: an overactive thyroid gland
- Malignant hypertension: a severe form of high blood pressure that can be life-threatening
- Placental mesenchymal dysplasia: a rare pregnancy complication with abnormal placental development
