Molar Pregnancy: Causes, Symptoms, Diagnosis and Treatment
Understand molar pregnancy — symptoms, causes, diagnosis and treatment options, explained clearly by Dr. Najeeb Layyous.
In short: A molar pregnancy is an abnormal pregnancy in which no healthy baby develops and the placenta turns into small cysts like a bunch of grapes; it may be complete or partial. Symptoms include vaginal bleeding, severe nausea and vomiting, early high blood pressure and an overactive thyroid. It is diagnosed by ultrasound and a high pregnancy hormone level, and treated by suction of the pregnancy tissue followed by monitoring of the hormone.
A molar pregnancy is an abnormal pregnancy that develops when there is a problem at the time of fertilization. Instead of a normal pregnancy, the tissue that forms resembles a cluster of grapes.
Molar pregnancies are categorized as partial moles or complete moles.
The word “mole” is simply the medical term used to describe this clump of abnormally growing tissue.
How common is it?
Molar pregnancy occurs in about 1 to 3 in every 1,000 pregnancies, with higher rates reported in parts of Asia compared to Western countries.
Genetic review
Complete moles have 46 chromosomes (diploidy): 85% are 46, XX and 15% are 46, XY, all of paternal origin. Most partial moles have 69 chromosomes (triploidy): 69, XXX; 69, XXY; or 69, XYY, including 23 chromosomes of maternal origin and 46 of paternal origin.
Signs and symptoms
- An early molar pregnancy may look just like a normal pregnancy at first.
- Molar pregnancies usually present with vaginal bleeding, abdominal pain, and cramps of the lower abdomen.
- The uterus is often larger than expected for the stage of pregnancy.
- The ovaries may be enlarged with cysts that cause abdominal pain.
- There may be more nausea and vomiting than expected (hyperemesis).
- Sometimes there is a rise in blood pressure along with protein in the urine, which may resemble early preeclampsia.
- Sometimes symptoms of hyperthyroidism are seen.
Causes and risk factors
The exact cause of this condition is not completely understood.
Risk factors may include:
- Defects in the egg
- Abnormalities within the uterus
- Nutritional deficiencies — diets low in protein, folic acid, and carotene
- Women under 20 or over 40 years of age have a higher risk
- Patients with a previous history of molar pregnancy
Diagnosis
Ultrasound examination is used to help diagnose a molar pregnancy before any treatment is done.
A partial mole is usually seen as a fetus together with a large placenta.
A complete mole presents with a picture often described as a “snowstorm” or “bunch of grapes.”
The definitive diagnosis is made by histological (laboratory tissue) examination of the products of conception.
Ultrasound findings
Complete mole
- Enlarged uterus
- May be seen as an intrauterine mass with cystic spaces without any associated fetal parts
“Snowstorm” or “bunch of grapes” type appearance.
- Bilateral theca lutein cysts may also be seen on ultrasound
Partial mole
- Usually presents as a fetus with a large placenta
- Cystic spaces within the placenta, which may not always be present
Coexisting molar pregnancy with a normal fetus
Rarely, in a twin pregnancy, one twin can be a complete mole while the other develops as a normal fetus. This type of pregnancy is usually at higher risk of ending in preterm labor or preeclampsia.
- Investigations
- Urine analysis
Thyroid function test
Beta-hCG levels are usually very highly elevated and are used both for diagnosis and for follow-up.
Baseline creatinine and electrolytes are checked, as these may become abnormal after severe vomiting.
- Liver function test, full blood count, and cross match
- Chest x-ray
Complications of molar pregnancy
Persistent mole or malignant complications are more common with a complete mole than with a partial mole.
Persistent or invasive disease (gestational trophoblastic neoplasia) needing chemotherapy develops in about 15% of complete moles and in only about 0.5–1% of partial moles; it is almost always curable when detected early by hCG follow-up.
Thyroid storm
Bleeding during evacuation
Preeclampsia and eclampsia
Treatment and outlook
Suction and curettage is the treatment of choice; ultrasound guidance during the procedure helps ensure the uterus is completely empty.
Rarely, treatment of a molar pregnancy involves hysterectomy, which may be considered in women over 40 years of age.
After treatment, the patient is followed up with serial beta-hCG levels until they return to normal.
Women are advised to avoid pregnancy until hCG follow-up is complete. For a partial mole this is usually a few weeks after hCG returns to normal; for a complete mole it is usually 6 months (counted from the evacuation if hCG returns to normal within 8 weeks, otherwise from the day it becomes normal). Contraceptive pills can be started straight after the evacuation.
If you have questions about a molar pregnancy diagnosis or need guidance on follow-up care, the team at Dr. Najeeb Layyous’s clinic is here to support you through every step.
Dr Najeeb Layyous F.R.C.O.G
Consultant Obstetrician, Gynecologist and Infertility Specialist
The finest doctor in Jordan — may God bless him and his whole medical team. A doctor in every sense of the word. I advise anyone planning a pregnancy to visit Dr. Najeeb Layyous. His manner is wonderful, always smiling, with the highest ethics; he gives every patient her due, and the patient’s comfort matters most to him. We had been to many doctors and none understood and treated my case except him. Special thanks to him and the whole team, and to Dina in particular — a lovely person. I recommend anyone considering IVF or pregnancy to visit his clinic.