A molar pregnancy is a type of gestational trophoblastic disease caused by the excessive growth of placental cells. It can lead to symptoms such as dark vaginal bleeding that looks like prune juice, nausea, and vomiting.

This condition is rare and is linked to genetic abnormalities in the fertilized egg, which cause the placenta to appear on an ultrasound as a cluster of grapes. In some rare cases, a molar pregnancy can develop into a type of cancer known as gestational choriocarcinoma.

Treatment for a molar pregnancy, also called a hydatidiform mole, is managed by an OBGYN and usually involves dilation and curettage (D&C), surgery to remove the uterus, or chemotherapy.

close up of ultrasound probe on woman's abdomen

Molar pregnancy symptoms

The main symptoms of molar pregnancy include:

Dark vaginal bleeding with a prune juice-like appearance;
Severe nausea and vomiting;
Passage of grape-like tissue through the vagina;
A uterus that is larger than expected for the gestational age;
Miscarriage between the 6th and 16th week of pregnancy.

In addition, symptoms of thyrotoxicosis such as tremors, excessive sweating, or heart palpitations can appear between the 14th and 16th weeks of pregnancy due to high beta-hCG levels.

Signs of preeclampsia may also develop before 20 weeks of pregnancy.

Is molar pregnancy cancer?

A molar pregnancy is a benign tumor that affects the placenta, but in some cases, it can lead to a type of cancer known as gestational choriocarcinoma.

This occurs when placental cells continue to multiply even after treatment and begin to invade other tissues in the body.

In these situations, treatment is typically done with chemotherapy.

Confirming a diagnosis

Diagnosis of a molar pregnancy is made by an OBGYN through an evaluation of symptoms, a pelvic exam, and imaging and lab tests.

The doctor will usually order a blood test to measure beta-hCG levels.

To confirm the diagnosis, an obstetric ultrasound is performed to examine the placenta and determine the type of molar pregnancy. This condition is usually diagnosed between the sixth and ninth week of pregnancy.

Possible causes

The causes of molar pregnancy are not completely understood, but it is believed to occur due to genetic abnormalities in the fertilized egg that result in abnormal placental tissue growth.

These genetic changes may be related to fertilization of an egg by two sperm cells or abnormalities in a sperm that fertilizes a healthy egg.

Risk factors

Certain factors may increase the risk of molar pregnancy, such as:

Pregnancy before age 20 or after age 35;
A history of molar pregnancy or other gestational trophoblastic disease;
A family history of hydatidiform mole;
Retained placental tissue after a miscarriage or ectopic pregnancy.

Lifestyle factors like smoking or having a diet low in vitamin A and animal fats may also increase the risk of developing a molar pregnancy.

Types of molar pregnancy

The two types of molar pregnancy are:

1. Complete molar pregnancy

A complete molar pregnancy occurs when two sperm fertilize an egg that has no nucleus, or when a single sperm duplicates itself. As a result, the embryo contains only the father’s genetic material.

This is the most common type of molar pregnancy, and in this case, no fetus develops, meaning there is no baby present.

2. Partial molar pregnancy

A partial molar pregnancy happens when a normal egg is fertilized by two sperm or by a diploid sperm that contains two sets of chromosomes instead of one.

This type of molar pregnancy involves the presence of fetal tissue, but a miscarriage usually occurs early in pregnancy because the fetus cannot survive.

Treatment options

Treatment for molar pregnancy should be started as soon as the condition is diagnosed, and involves removing the abnormal tissue under the supervision of an OBGYN.

The main treatment options include:

1. Dilation and curettage

Dilation and curettage (D&C) is performed to empty the uterus and remove the placenta and all abnormal tissue. This procedure is usually recommended for women who wish to preserve fertility.

If the woman has Rh-negative blood, the doctor should administer Rh immunoglobulin to prevent complications in future pregnancies, such as hemolytic disease of the newborn.

2. Hysterectomy

A hysterectomy, which is the surgical removal of the uterus, is generally recommended for women who do not wish to become pregnant again.

It may also be indicated in cases of complete molar pregnancy or when there is an increased risk of developing cancer.

3. Medication

If cancer (gestational choriocarcinoma) develops, a doctor may prescribe chemotherapy drugs such as methotrexate or actinomycin-D.

Chemotherapy helps eliminate any cancerous cells that may remain after surgery and prevents them from spreading to other parts of the body.

In some cases, radiation therapy may also be recommended.

4. Regular medical follow-up

Regular medical follow-up after treatment is essential to confirm that the condition has resolved completely or to detect whether it persists or has progressed to cancer.

In cases of complete molar pregnancy, blood tests to measure beta-hCG levels are typically performed every 7 to 15 days until three consecutive tests show normal or negative results.

After this initial phase, follow-up visits and tests are usually recommended once a month for six months.

For partial molar pregnancy, a beta-hCG test is typically done one month after treatment.

5. Pregnancy and contraception after treatment

Women should avoid becoming pregnant until follow-up is complete, as pregnancy can interfere with monitoring beta-hCG levels.

It is generally advised to wait at least six months after beta-hCG levels return to normal before attempting conception.

During this period, effective contraception is strongly recommended. Hormonal methods such as birth control pills, the patch, or injections are considered safe and effective. However, intrauterine devices (IUDs) should be avoided until hCG levels have normalized and the uterus has completely healed.

Molar Pregnancy: Symptoms, Causes & Treatment