What is a molar pregnancy?

A molar pregnancy happens when a fertilized egg develops into a growth called a mole instead of into a normal embryo. You may still have typical pregnancy symptoms in the beginning. But eventually you'll have bleeding and other symptoms that indicate something is wrong.

It can be scary and sad to lose a pregnancy this way. But as long as you get proper treatment, you're unlikely to have any long-term physical consequences.

How common are molar pregnancies?

About 1 in 1,500 pregnancies in the United States is a molar pregnancy. If you're under age 20 or over age 35, or if you've had a previous molar pregnancy, or two or more miscarriages, your chances of having a molar pregnancy are higher. Women of Southeast Asian descent also seem to have a higher risk of molar pregnancy.

What causes a molar pregnancy?

A molar pregnancy happens when there are certain problems with the genetic information (the chromosomes) in the fertilized egg at conception. The result is that the egg may develop into a growth with no embryo (this is called a complete mole) or an abnormal embryo (a partial mole).

In normal pregnancies, the fertilized egg contains 23 chromosomes from the father and 23 from the mother. This isn't the case with a molar pregnancy.

In most complete molar pregnancies, the fertilized egg contains two copies of the chromosomes from the father and none from the mother. In this case, there's no embryo, amniotic sac, or any normal placental tissue. Instead, the placenta forms a mass of cysts that looks like a cluster of grapes.



In most partial molar pregnancies, the fertilized egg has the normal set of chromosomes from the mother and two sets from the father, so there are 69 chromosomes instead of the normal 46. (This can happen when chromosomes from the sperm are duplicated or when two sperm fertilize the same egg.)

In a partial molar pregnancy, there's some normal placental tissue among the cluster of abnormal tissue. The embryo does begin to develop, so there may be a fetus or just some fetal tissue or an amniotic sac. But even if a fetus is present, in most cases it's so abnormal that it can't survive.

How would I know if I had a molar pregnancy?

Early on, you might have typical pregnancy symptoms, but at some point you'll begin to have some spotting or heavier bleeding. It might be bright red or a brownish discharge, continuous or intermittent, light or heavy. This bleeding could start as early as six weeks into your pregnancy or as late as 12 weeks.

You might also have severe nausea and vomiting, abdominal cramping, and abdominal swelling (because your uterus may grow more rapidly than usual).



Some women develop preeclampsia before midpregnancy if they have an undiagnosed molar pregnancy. However, because ultrasound helps practitioners diagnose molar pregnancies earlier these days, it's rare to carry one long enough for this condition to develop.

Call your doctor or midwife right away if you have any spotting or bleeding during your pregnancy. These symptoms don't necessarily signal a molar pregnancy, but your practitioner will probably order an ultrasound to find out what's causing them and may do a blood test to measure your levels of the hormone hCG. If you do have a molar pregnancy, the ultrasound will show cysts that look like a cluster of grapes in your uterus, and your levels of hCG will be higher than normal.

What's the treatment for a molar pregnancy?

If you're diagnosed with a molar pregnancy, you'll need a D&C (dilation and curettage) or suction curettage to remove the abnormal tissue. This procedure can be done under general or regional anesthesia, or you can be sedated intravenously.



To perform a D&C, the doctor inserts a speculum into the vagina, cleans the cervix and vagina with an antiseptic solution, and dilates the cervix with narrow metal rods. She then passes a hollow plastic tube through the cervix and suctions out the tissue from the uterus. Finally, she uses a spoon-shaped instrument called a curette to gently scrape the rest of the tissue from the walls of the uterus.



You'll most likely also have a chest X-ray afterward to see whether abnormal cells from the molar pregnancy have spread to your lungs. It's rare for these cells to spread to other parts of the body, but if they do, the lungs are the most common site.



Your practitioner will then want to monitor your levels of hCG once a week to make sure they're declining – an indication that no molar tissue remains. Once the levels go down to zero for a few weeks in a row, you'll still have to have them checked every month or two for the next year.

Occasionally, abnormal cells remain after the tissue is removed. This happens in up to 11 percent of women with partial moles and 18 to 29 percent of women with complete moles and it's called persistent gestational trophoblastic neoplasia.

In most cases, the persistent moles can be treated with chemotherapy. But a very small number of them (1 in 20,000 to 40,000) will advance to a form of malignant cancer called gestational choriocarcinoma.

With prompt and appropriate treatment, nearly 100 percent of cases of gestational choriocarcinoma are curable when it hasn't spread beyond the uterus. Even in rare cases in which the abnormal cells have spread to other organs, 80 to 90 percent of cases can be cured. After you're in complete remission, you'll need to have your hCG levels monitored for a year, and possibly other regular testing.

(One thing to note: If you decide you don't want another pregnancy, you might opt for a hysterectomy instead of a D&C, because it lowers your risk that the abnormal cells will return. Women over 40 who have complete moles are often offered this option because they're at particular risk.)

When can I try to get pregnant again?

No matter what kind of treatment you've received, you'll need to wait a year after your hCG levels go back down to zero before trying to get pregnant again. If you got pregnant before then, your hCG levels would rise and it would be impossible for your practitioner to tell whether abnormal tissue was growing back.



The good news is that having a molar pregnancy doesn't affect your fertility or ability to have a normal pregnancy, even if you've had chemotherapy. You're not at any increased risk for stillbirth, birth defects, preterm delivery, or other complications. And your odds of having another molar pregnancy are only 1 to 2 percent. You'll have a first-trimester ultrasound in any subsequent pregnancies to make sure all is well.

How can I cope with my sense of fear and loss?

Having a molar pregnancy can be frightening. Like any woman who has miscarried, you're dealing with the loss of your pregnancy, but in this case, you've had an unusual condition that most people have never heard of and you're concerned for your own health as well.

You'll have to go in for at least a year of weekly or monthly follow-up visits before you can try to conceive again, and you may be very anxious about the possibility of having persistent abnormal cells. If you do have persistent disease, treatment with chemotherapy can be very draining and can delay your next pregnancy even longer.



You may feel devastated by your experience. Your partner may also be feeling sad or helpless and may have trouble figuring out how to express those feelings or how to be supportive. It's perfectly okay to seek counseling if you think it will help you or your partner. Ask your caregiver where to get counseling or find support groups. Get support and advice on molar pregnancy or in the BabyCenter Community.