Molar pregnancy

A **molar pregnancy** (also called **hydatidiform mole**) is a rare pregnancy complication. It happens when abnormal tissue grows inside the uterus instead of a normal fetus. This tissue comes from cells that would normally become the placenta.

## What is a molar pregnancy?

A molar pregnancy is a type of gestational trophoblastic disease. It occurs when there are problems with the genetic material during fertilization. Instead of a normal pregnancy developing, abnormal tissue grows rapidly inside the uterus. This tissue looks like small grape-like clusters.

## Types

There are two main types of molar pregnancy:

### Complete molar pregnancy

In a complete molar pregnancy, there is no normal fetus or amniotic sac. This happens when:
- An egg with no genetic material gets fertilized by one or two sperm
- The result is tissue with only the father's genetic material
- All the chromosomes come from the father
- Under ultrasound, it looks like a "snowstorm" pattern
- This type has a higher risk of becoming cancerous

### Partial molar pregnancy

In a partial molar pregnancy:
- There may be some fetal tissue, but it cannot develop normally
- This happens when a normal egg is fertilized by two sperm
- The fetus has too many chromosomes (69 instead of the normal 46)
- The fetus cannot survive and is usually lost early in pregnancy
- There may be some normal placental tissue mixed with abnormal tissue

## Signs and symptoms

Early signs of a molar pregnancy are similar to normal pregnancy, but may include:
- Vaginal bleeding during the first 3 months of pregnancy
- Severe nausea and vomiting (worse than normal pregnancy)
- A uterus that grows faster and larger than expected
- Very high levels of hCG hormone in blood tests
- High blood pressure early in pregnancy
- Ovarian cysts caused by high hormone levels
- No fetal heartbeat heard on ultrasound
- Passing grape-like tissue from the vagina

Some women may have no symptoms at first.

## Diagnosis

Doctors use several tests to diagnose molar pregnancy:
- **Ultrasound examination** - Shows the characteristic "snowstorm" pattern
- **Blood tests** - Measure very high hCG hormone levels
- **Physical examination** - Check uterus size and other symptoms
- **Tissue examination** - If grape-like tissue is passed, it can be tested

Early diagnosis is important for proper treatment and to prevent complications.

## Treatment

Treatment for molar pregnancy includes:

### Immediate treatment

- **Suction curettage** - A surgical procedure to remove all abnormal tissue from the uterus
- This is usually done under anesthesia in a hospital
- The removed tissue is examined under a microscope

### Follow-up care

After treatment, doctors closely monitor patients because:
- hCG hormone levels must return to zero
- Blood tests are done weekly, then monthly for up to one year
- Chest X-rays may be done to check for spread to lungs
- Patients should not get pregnant for at least 6 months to 1 year
- Birth control is strongly recommended during this time

## Complications and risks

Molar pregnancy can lead to serious complications:

### Immediate risks

- Heavy bleeding
- High blood pressure
- Anemia from blood loss
- Thyroid problems

### Long-term risks

- **Persistent gestational trophoblastic disease** - When abnormal cells remain after treatment
- **Choriocarcinoma** - A rare but serious type of cancer that can develop
- Cancer can spread to other parts of the body including:
    - Lungs
    - Liver
    - Brain
    - Other organs

This is why long-term follow-up care is very important.

### Risk factors

Some factors that may increase risk include:
- Age under 20 or over 35 years
- Previous molar pregnancy
- Certain ethnic backgrounds
- Diet low in vitamin A and protein

### Outlook

- Most molar pregnancies are cured with proper treatment
- About 90% of patients have no further problems
- Future normal pregnancies are usually possible
- Early detection and treatment give the best results

## When to see a doctor

See a doctor right away if you have:
- Heavy vaginal bleeding during pregnancy
- Severe nausea and vomiting
- Passage of grape-like tissue
- No fetal movement when expected
- Very rapid uterus growth

## References

1. Molar Pregnancy: Early Diagnosis, Clinical Management, and the Central Role of Referral Centers. PMC12346673. 2025. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC12346673/
2. Diagnosis and Surgical Treatment of Hydatidiform Mole. PMC12386084. 2025. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC12386084/
3. Hydatidiform Mole - StatPearls. NCBI Bookshelf. 2024. Available at: https://www.ncbi.nlm.nih.gov/books/NBK459155/
4. Advances in the diagnosis and early management of gestational trophoblastic disease. PMC9978730. 2022. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9978730/