What is a Molar Pregnancy?

A positive pregnancy test is often followed by the joy of a newborn baby 9 months later. But there are times when pregnancy ends in a loss. A molar pregnancy is one of those.

During a healthy pregnancy, the placenta grows inside your uterus. It nourishes your baby through the umbilical cord. With a molar pregnancy, tissue in the uterus becomes an abnormal mass or tumor instead of a placenta.

There are two types of molar pregnancy -- partial and complete. A partial one is when both the placenta and embryo (fertilized egg) are abnormal. In a complete molar pregnancy, there’s an abnormal placenta, but no embryo.

What Causes a Molar Pregnancy?

It’s due to problems with the fertilized egg. Normal human cells contain 23 pairs of chromosomes -- one set from the mother and the other from the father. These structures carry information that tells the body’s cells what to do. In a molar pregnancy, there’s an extra set of chromosomes that comes from the father. When this happens, a fertilized egg can’t survive. It usually dies a few weeks into the pregnancy.


At first, your pregnancy might seem normal. But over time, you may start to notice the following:

  • Bleeding from your vagina in the first 3 months of pregnancy
  • Watery brown discharge
  • Sacs (they look like clusters of grapes) that pass out of your vagina
  • Nausea and vomiting that are more frequent or severe than what’s normal during pregnancy
  • Lots of pressure or pain in your pelvis

Call your doctor if you have these or any other unusual symptoms during pregnancy.

How Is It Diagnosed?

Your doctor may find out when he does an ultrasound test. This is the device that uses sound waves to look inside your uterus. He may also detect a problem through a blood test. When you’re pregnant, levels of the hormone HCG (human chorionic gonadotropin) increase. If you have a molar pregnancy, your HCG level is often much higher than it should be.


Who Is Most at Risk?

In the United States, molar pregnancy occurs in about 1 out of every 1,000 pregnancies. Certain things may increase the chances it will happen:

  • You’re younger than 20 or older than 35.
  • You’ve had a molar pregnancy before.
  • You’ve had a pregnancy loss before.
  • You’ve had difficulty conceiving or infertility problems

Can It Be Prevented?

The only way to be certain you won’t have a molar pregnancy is not to get pregnant. If you’ve had a molar pregnancy in the past, talk to your doctor. Ask him about the chances of it happening again. And find out how you’ll be monitored if you do get pregnant.

How Is It Treated?

Your doctor may use a procedure called dilation and curettage (D&C). This is often the treatment for pregnancy loss due to any reason. During this procedure, your doctor opens your cervix with special tools and removes the tissue from your uterus. This is the best option for you if you want to get pregnant again.

After a D&C, your doctor may do blood tests several times over the next few months. He will look to see whether your HCG levels are getting back to normal.

If you don’t want to get pregnant again, then you may consider a total hysterectomy. That’s surgery to remove your uterus.

In rare cases, a complete molar pregnancy can lead to a condition called persistent gestational trophoblastic disease (GTD). This means the abnormal tissue grows outside your uterus and into the layer of muscle below it. A D&C won’t work because it only removes tissue within the uterus. You may need to have a hysterectomy or receive chemotherapy (“chemo”) to treat persistent GTD.

A molar pregnancy can also lead to a cancerous form of GTD called choriocarcinoma. You’ll need to have chemo to treat it.

After a molar pregnancy, your doctor might recommend that you don’t conceive for 1 year. Pregnancy increases HCG levels, so it would be hard for him to know whether the rise in hormones is due to that, abnormal tissue that’s still in your body, or choriocarcinoma.

WebMD Medical Reference Reviewed by Trina Pagano, MD on October 31, 2018



March of Dimes: “Molar Pregnancy.”

American Cancer Society: “Gestational Trophoblastic Disease.”

American Congress of Obstetricians and Gynecologists: “Ultrasound Exams,” “Dilation and Curettage.”

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