1. Pregnancy
  2. Pregnancy health
  3. Complications

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Molar Pregnancy Causes, Symptoms, Risk Factors, and Treatment

Molar pregnancies belong to a group of diseases called gestational trophoblastic diseases (GTD). These type of pregnancies are also referred to as hydatidiform moles and they are the most common GTD diseases.

Although the incidences of molar pregnancies are significantly low in most countries occurring in only 1 of every 1,000 pregnancies, studies show that women of Asian origin most frequently experience a molar pregnancy, especially those who are below 20 years and above 35 years of age. This trend is attributed to socioeconomic and nutritional factors.

What is a molar pregnancy?

A molar pregnancy occurs when a fertilized egg fails to develop into a normal embryo despite implanting into the uterus. 

In a healthy pregnancy, the placenta, which is responsible for nourishing the baby, develops in the uterus. In a molar pregnancy, the tissue inside the uterus does not develop into a healthy placenta.

Molar pregnancies can be classified as either partial and complete depending on the state of the placenta. 

Partial molar pregnancy

A partial molar pregnancy occurs when there is a problem with the egg that has been fertilized. There are 23 pairs of chromosomes in a normal human cell. One set is from the mother, the other one is from the father. But in case of partial molar pregnancy there is an additional set of chromosomes from the father

In addition, in a partial molar pregnancy, the placenta is larger than normal and cystic. In the event of triploidy, the fertilized egg might develop into a nonviable fetus that can’t be carried to term. They frequently end in miscarriage. Non-triploidy partial molar pregnancies are extremely rare, but can sometimes be successfully carried to term, depending on the cause and the state of the fetus.

Complete molar pregnancy

A complete molar pregnancy or complete mole is a pregnancy that contains only paternal chromosomes and zero maternal chromosomes.  

Every female egg contains 23 chromosomes, but some eggs lose their chromosomes.

When a sperm fertilizes an egg that contains zero chromosomes, it duplicates its own chromosomes. The resulting pregnancy has no embryo and has an abnormal placenta. The fertilized egg does not develop into an embryo because it does not contain the chromosomes that help form the embryo.

Molar pregnancy symptoms

Some symptoms of molar pregnancy include: 

Vaginal bleeding or spotting during the first trimester

It is common for a pregnant person to experience some spotting (light bleeding) during their first trimester. This is referred to as implantation bleeding and usually it occurs a few days after conception. 

But with a molar pregnancy, the bleeding is not light, but heavy. Since the bleeding is heavy and occurs during the first trimester, some people mistakenly assume it’s a miscarriage.   

Vomiting and nausea

Vomiting and nausea are common symptoms of early pregnancy. But in the case of molar pregnancies, these symptoms are more severe and frequent than in healthy pregnancies.  

High hCG levels

High levels of the hormone hCG (human chorionic gonadotropin) indicate a trophoblastic growth, which may suggest a molar pregnancy.

Molar pregnancy ultrasound

The diagnosis of a molar pregnancy is done using ultrasound testing. This is the surest way of knowing if you have a hydatidiform mole. 

A blood test can also help diagnose a molar pregnancy by checking the hCG levels in the bloodstream. In a normal pregnancy, the hCG levels increase and this is normal. But if these levels are higher than what is considered normal in a healthy pregnancy, this may indicate a molar pregnancy. 

Molar pregnancy treatment

A molar pregnancy is unviable, which means it can’t be carried to term. Early treatment can help prevent complications and lower the risk of developing certain cancers. 

There are two treatment options that are mainly used to treat a molar pregnancy: Dilatation and Curettage (D&C), and hysterectomy.

D&C removes defective tissue from the uterus.Your doctor uses small instruments or a medication to open (dilate) your cervix. The doctor will then dilate your cervix and use something called a curette to remove the defective tissue from your uterus. This is the most ideal treatment option for women who want to conceive again. 

After treatment, follow-up may be necessary to monitor your hCG levels and make sure they removed all the molar tissue. Usually these follow-ups happen once a month for at least six months, but they may need to continue monthly testing for up to a year.

After a molar pregnancy, your doctor might recommend that you don’t conceive for 1 year.

Risk factors and complications

Risk factors that might increase a woman’s risk of getting a molar pregnancy include: 

  • Age: women who are over 35 years or below 20 years of age are at greater risk of having a molar pregnancy. This is one reason why when women reach a certain age, they are sometimes advised to freeze their eggs for a future pregnancy.   
  • Previous molar pregnancy: women who have had a molar pregnancy are at a higher risk of having another one than women who have never had one.  
  • Previous miscarriage: Some women develop a molar pregnancy after a miscarriage. 

Although rare, molar pregnancies can sometimes cause complications. These complications include rare forms of cancers.  

Getting pregnant after a molar pregnancy

It is possible to get pregnant after the successful treatment of a molar pregnancy. But before you get the green light from your physician, you’ll need to attend all your follow-up appointments. Follow-up tests to check your hCG levels are necessary to ensure that the treatment is working and there are no other complications.    

If you want to get pregnant again, and you have some concerns, your doctor can offer you advice and information about your health.