Pregnancy happens after an egg is fertilized and burrows into the womb. Sometimes, though, these delicate beginning stages can get mixed up. When this happens, a pregnancy may not go the way it should — and this can be heartbreaking, even though it’s no one’s fault.

A molar pregnancy occurs when the placenta doesn’t develop normally. Instead, a tumor forms in the uterus and causes the placenta to become a mass of fluid-filled sacs, also called cysts. About 1 in every 1,000 pregnancies (0.1 percent) is a molar pregnancy.

This kind of pregnancy doesn’t last because the placenta typically can’t nourish or grow a baby at all. In rare cases, it may also lead to health risks for mom.

A molar pregnancy is also called a mole, a hydatidiform mole, or gestational trophoblastic disease. You can have this pregnancy complication even if you have had a typical pregnancy before. And, the good news — you can have a completely normal, successful pregnancy after having a molar pregnancy.

There are two kinds of molar pregnancy. Both have the same result, so one isn’t better or worse than the other. Both kinds are usually benign — they don’t cause cancer.

A complete mole happens when there’s only placenta tissue growing in the womb. There’s no sign of a fetus at all.

In a partial mole, there is placenta tissue and some fetal tissue. But the fetal tissue is incomplete and could never develop into a baby.

You can’t control whether or not you have a molar pregnancy. It’s not caused by anything you did. A molar pregnancy can happen to women of all ethnicities, ages, and backgrounds.

It sometimes happens because of a mix-up at the genetic — DNA — level. Most women carry hundreds of thousands of eggs. Some of these might not form correctly. They’re usually absorbed by the body and put out of commission.

But once in a while an imperfect (empty) egg happens to get fertilized by a sperm. It ends up with genes from the father, but none from the mother. This can lead to a molar pregnancy.

In the same way, an imperfect sperm — or more than one sperm — may fertilize a good egg. This can also cause a mole.

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A molar pregnancy is also known as a hydatidiform mole. Surgical removal is the mainstay of treatment for this condition. Image source: Wikimedia

Risk factors

There are some risk factors for a molar pregnancy. These include:

  • Age. Although it can happen to anyone, you may be more like to have a molar pregnancy if you’re younger than 20 or older than 35 years.
  • History. If you’ve had a molar pregnancy in the past, you’re more likely to have another one. (But again — you can also go on to have a successful pregnancy.)

A molar pregnancy may feel just like a typical pregnancy at first. However, you’ll likely have certain signs and symptoms that something is different.

  • Bleeding. You may have bright red to dark brown bleeding in the first trimester (up to 13 weeks). This is more likely if you have a complete molar pregnancy. The bleeding might have grape-like cysts (tissue clots).
  • High hCG with severe nausea and vomiting. The hormone hCG is made by the placenta. It’s responsible for giving many pregnant women a certain amount of nausea and vomiting. In a molar pregnancy, there may be more placenta tissue than normal. The higher levels of hCG might lead to severe nausea and vomiting.
  • Pelvic pain and pressure. Tissues in a molar pregnancy grow faster than they should, especially in the second trimester. Your stomach may look too large for that early stage in pregnancy. The fast growth can also cause pressure and pain.

Your doctor may also find other signs like:

Sometimes a molar pregnancy is diagnosed when you go for your usual pregnancy ultrasound scan. Other times, your doctor will prescribe blood tests and scans if you have symptoms that might be caused by a molar pregnancy.

A pelvis ultrasound of a molar pregnancy will typically show a grape-like cluster of blood vessels and tissue. Your doctor may also recommend other imaging — like MRI and CT scans — to confirm the diagnosis.

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A molar pregnancy, although not dangerous by itself, has the potential to become a cancer. Image source: Wikimedia

High levels of hCG in the blood might also be a sign of a molar pregnancy. But some molar pregnancies may not raise hCG levels — and high hCG is also caused by other standard kinds of pregnancies, like carrying twins. In other words, your doctor won’t diagnose a molar pregnancy based on hCG levels alone.

A molar pregnancy can’t grow into a normal, healthy pregnancy. You must have treatment to prevent complications. This can be really, really hard news to swallow after the initial joys of that positive pregnancy result.

With the right treatment, you can go on to have a successful pregnancy and healthy baby.

Your treatment may involve one or more of the following:

Dilation and curettage (D&C)

With a D&C, your doctor will remove the molar pregnancy by dilating the opening to your womb (cervix) and using a medical vacuum to remove the harmful tissue.

You’ll be asleep or get local numbing before you have this procedure. Although a D&C is sometimes done as an outpatient procedure at a doctor’s office for other conditions, for a molar pregnancy it’s typically done at a hospital as an inpatient surgery.

Chemotherapy drugs

If your molar pregnancy falls into a higher risk category — due to cancer potential or because you have had difficulty getting proper care for whatever reason — you may receive some chemotherapy treatment after your D&C. This is more likely if your hCG levels don’t go down over time.


A hysterectomy is surgery that removes the entire womb. If you don’t wish to get pregnant again, you might choose this option.

You’ll be fully asleep for this procedure. A hysterectomy is not a common treatment for a molar pregnancy.


If you have Rh-negative blood, you’ll receive a drug called RhoGAM as part of your treatment. This prevents some complications related to developing antibodies. Be sure and let your doctor know if you have A-, O-, B-, or AB- blood type.


After your molar pregnancy is removed, you’ll need more blood tests and monitoring. It’s very important to make sure that no molar tissue was left behind in your womb.

In rare cases, molar tissue can regrow and cause some types of cancers. Your doctor will check your hCG levels and give you scans for up to a year after treatment.

Later-stage treatment

Again, cancers from a molar pregnancy are rare. Most are also very treatable and have a survival rate of up to 90 percent. You may need chemotherapy and radiation treatment for some cancers.

If you think you’re pregnant, see your doctor right away. As with many things, the best way to prevent complications from a molar pregnancy is to get diagnosed and treated as early as possible.

After treatment, see your doctor for all follow-up appointments.

It’s best to wait to get pregnant again for up to a year after treatment. This is because pregnancy can mask any rare, but possible complications after a molar pregnancy. But talk to your doctor — your situation is unique, just like you are.

Once you’re completely in the clear, it’ll likely be safe for you to get pregnant again and have a baby.

Also know that cancers and complications from molar pregnancies are very rare. In fact, the University of Pennsylvania Medical School advises that prior molar pregnancies or other risk factors for developing the related cancerous tumors shouldn’t factor into family planning.

Molar pregnancies aren’t common, but they can happen to women of all ages and backgrounds. A molar pregnancy can be a long and emotionally draining experience.

The treatment and waiting period can also take a toll on your emotional, mental, and physical health. It’s important to take the time to grieve for any kind of pregnancy loss in a healthy way.

Ask your doctor about support groups. Reach out to other women who have gone through a molar pregnancy. Therapy and counseling can help you look forward to a healthy pregnancy and baby in the not-so-distant future.