Molar Pregnancy : Types, Causes, Symptoms, Treatment, Diagnosis, Risks

Molar Pregnancy : Types, Causes, Symptoms, Treatment and Diagnosis
Molar Pregnancy : Types, Causes, Symptoms, Treatment and Diagnosis


A molar pregnancy is also called a hydatidiform mole. It is a rare complication of pregnancy that occurs due to abnormal growth of cells, known as trophoblasts, that develop into the placenta. Molar pregnancy is of two types – complete and partial molar pregnancy.

The blog delves into molar pregnancy types, causes, treatment options, and risks.

What is a molar pregnancy?

Before understanding molar pregnancy, it is essential to get an insight into pregnancy. A woman is pregnant once the fertilized egg is inside the uterus. However, in the early stages of pregnancy, the placenta fails to develop, forming a mass of fluid-filled sacs in the uterus. These sacs are called cysts. It is called a molar pregnancy.

Molar pregnancy does not last as the placenta cannot nourish and grow a baby. However, it may also affect the mother’s health in rare cases. About 1 in every 1,000 pregnancies is a molar pregnancy.

What are the types of molar pregnancy?

There are two types of molar pregnancy, namely partial and complete molar pregnancy.

  1. Partial molar pregnancy: A placenta and fetus are partially developed in this pregnancy. The incomplete fetal tissue does not develop into a baby.
  2. Complete molar pregnancy: When there is only a developed placenta and an absence of a fetus is called a complete molar pregnancy. 

A molar pregnancy can have serious complications — including a rare form of cancer — and requires early treatment.

What are the causes of a molar pregnancy?

The cause of a molar pregnancy is a genetic error during the fertilization of an egg by the sperm. Typically in a normal pregnancy, a placenta develops to nourish and grow the baby. But in molar pregnancy, a benign tumour develops that cannot nourish or grow a fetus ,instead of a placenta. 

Scientifically speaking, there are 23 pairs of chromosomes in healthy human cells. The fetus equally receives these chromosomes from the mother and father. 

When an empty egg gets fertilised by one or two sperm, getting all the material from the father, it is called a complete molar pregnancy. In this pregnancy, the mother’s chromosomes present in the egg are either lost or deactivated, and the chromosomes from the father are duplicated. However, in a partial or incomplete pregnancy, the mother’s chromosomes remain the same, while that of the father offers two sets of chromosomes.

When to seek medical advice?

Although a molar pregnancy may show signs of a normal pregnancy, most molar pregnancies exhibit specific signs and symptoms. These include:

  • Vaginal bleeding that occurs in the first trimester. The patient may notice dark brown to bright red vaginal bleeding
  • Extreme nausea and vomiting
  • In certain cases, the passage of grape like cysts in the vagina
  • Pain and pressure in the pelvic area

If you know or are experiencing any of the above-mentioned signs and symptoms of molar pregnancy, consult your doctor or healthcare provider immediately.


What are the symptoms of a molar pregnancy?

At first, a woman may feel like she has a healthy pregnancy. However, as the pregnancy progresses, a pregnant woman may notice the following:

  1. Vaginal bleeding: A pregnant woman may experience bright red to dark brown bleeding in the first trimester. The bleeding may include grape-like cysts.
  2. Increased hCG level with nausea and vomiting: The hCG hormone is responsible for placenta development, nausea, and vomiting. However, in molar pregnancy, women develop more placental tissue than usual, leading to severe nausea and vomiting.
  3. Increased pain and pressure in the pelvis: In a molar pregnancy, tissue growth is faster than typical pregnancy, particularly during the second trimester. Therefore, the stomach may appear larger than usual, causing pressure and pain.

Other signs include:

  • Increase in blood pressure
  • Rapid growth in the uterus that does not correspond to the gestational age of pregnancy
  • Development of preeclampsia – a condition that occurs after 20 weeks of pregnancy. It increases high blood pressure and protein in the urine.
  • Iron deficiency
  • Ovarian cysts and overactive thyroid

What is the risk factor for a molar pregnancy?

The various risk factors for a molar pregnancy include:

  1. Age: A woman younger than 20 or over 35 is more likely to experience a molar pregnancy. Although, anyone can experience a molar pregnancy. 
  2. History: If a woman has experienced a molar pregnancy before, the chances of experiencing another molar pregnancy are high. However, it is important to note that women with past molar pregnancies can also experience successful, normal pregnancies. 

What are molar pregnancy complications?

Once the molar pregnancy is removed, there are chances of the molar tissues remaining. In such cases, the tissues continue to grow. It is known as persistent gestational trophoblastic neoplasia (GTN). It typically occurs in 15-20% of complete molar pregnancies and up to 5% of partial molar pregnancies. A woman who experiences persistent GTN is treatable with chemotherapy or a hysterectomy. In rare cases, a GTN may develop into a cancerous form known as choriocarcinoma and spread to other organs. 

What are the treatment options for a molar pregnancy?

As mentioned earlier, a fetus fails to thrive and grow in molar pregnancy compared to a healthy pregnancy. Therefore, it is vital to get treated to prevent further complications. The doctor may recommend one or a combination of the following treatment options. 

  1. Dilation and curettage (D&C): The doctor dilates the cervix and uses a medical vacuum to remove the cysts. Thus, ending the molar pregnancy. It is an inpatient procedure, and the doctor will administer local anaesthesia to the patient.  

After the procedure, the patient may continue to show hCG hormones in the blood. In such cases, the doctor may monitor their hCG levels for close to a year and may need additional treatments to ensure no molar tissues remain. As pregnancy hCG hormones increase during normal pregnancy, a healthcare provider may recommend that the patient waits for 6 to 12 months before conceiving. The doctors may provide a reliable and effective form of birth control.

  1. Hysterectomy: It is an uncommon treatment option. A hysterectomy is when the entire womb gets removed. This option is opted for when the patient does not want to conceive again. 
  2. RhoGAM: If the patient is Rh-negative blood group, the doctor prescribes RhoGAM as a part of the treatment to prevent complications associated with developing antibodies. It is crucial to let the doctors know about the blood type.

How is molar pregnancy diagnosed?

The different ways to diagnose a molar pregnancy include an ultrasound and a blood test. A blood test shows elevated hCG levels that are often higher than normal. 


Although hearing the news of molar pregnancy may be heartbreaking, it is vital to understand that there is treatment, and the subsequent pregnancy may not develop into a molar pregnancy. 

Frequently Asked Questions (FAQs)

Is molar pregnancy preventable?

If a woman has a previous molar pregnancy, she needs to consult an expert before trying to conceive again. The doctor may recommend waiting for six months to a year before trying to get pregnant. However, the risk of recurrence is low. But it is higher than in patients with no history of molar pregnancy.

How common is a molar pregnancy?

It is estimated that less than 1 percent of pregnancies are molar pregnancies.