What Is A Molar Pregnancy?

A Molar Pregnancy (also called gestational trophoblastic disease (GTD) or hydatidiform mole) is a placental abnormality that is caused by a problem during the fertilization process of sperm and egg. This non-viable - but fertilized egg - implants into the uterine lining (the endometrium) and grows until it is detected by medical personnel.

A molar pregnancy may be called a "missed miscarriage" as the pregnancy is non-viable and was not immediately expelled.

Read more about miscarriage here.

Most molar pregnancies do not contain fetal material. Instead, this non-viable egg begins to grow grape-like clusters of cysts inside the uterus. This material grows much faster than normal pregnancies, intensifying pregnancy symptoms in the mother.

There are two types of Molar Pregnancy: Complete Mole and Partial Mole.

A molar pregnancy can lead to very severe complications - including cancer - and requires immediate treatment.

What Causes A Molar Pregnancy?

A molar pregnancy can develop after a non-viable (meaning, unable to create a fetus) fertilized egg is implanted into the uterine wall.

In this non-viable egg, there is an extra set of chromosomes in the fertilized egg (from the sperm), which causes an error in what would normally be a developing fetus. This error causes the placenta to grow into a mass of cysts.

In normal human cells, we each have 23 pairs of chromosomes - one set from each parent. This means that cells in a normal pregnancy have 46 chromosomes.

In a complete molar pregnancy, all of the chromosomes of the fertilized egg come from the father. This may happen shortly after the egg is fertilized, when the chromosomes from the mother's egg (ova) are lost or inactivated, and the father's chromosomes are duplicated. The ova may have been inactive or had no nucleus.

In an incomplete - or partial - molar pregnancy, the maternal chromosomes remain in the fertilized egg, however, the father provides two sets of chromosomes, leading the fertilized egg to have 69 - rather than 45 - chromosomes. A partial molar pregnancy may be caused by the father's chromosomes being duplicated or if a pair of sperm fertilize the egg.

What Is A Complete Molar Pregnancy?

A complete molar pregnancy contains only placental parts - no fetal material - and can be caused by a sperm fertilizing an egg (ova) without a nucleus.

The placenta grows and produces large amounts of human chorionic gonadotropin (hCG), causing the uterus to fill with a tumor that appears much like a large collection of grape-like clusters of cells.

What Is A Partial Molar Pregnancy?

In a partial molar pregnancy, the mass that grows in the uterus contains the abnormal grape-like clusters of cells as well as a very defective embryo. In a partial molar pregnancy, the fetal material will be overtaken by the growing mass of abnormal cells in the uterus quickly.

In a very rare type of partial molar pregnancy, twins are conceived. One of the twins will develop normally while the other turns into a molar pregnancy. The healthy embryo will, sadly, be quickly overcome by the abnormal growth.

Who Is At Risk For Developing A Molar Pregnancy?

Thankfully, molar pregnancies are uncommon, only occurring in one of every 1,000 pregnancies. Risk factors for a molar pregnancy include the following:

  • Age: Advanced maternal age over age 25 or younger than 20 years old.
  • Previous molar pregnancies - having a prior molar pregnancy increases risks for developing another molar pregnancy. On average, 1-2 out of 100 women who have had a molar pregnancy will develop another molar pregnancy.
  • Ethnicity: Women who are from Southeast Asia, Mexico and the Philippines have increased risks for development of a molar pregnancy.
  • History of Miscarriage (non-molar)

What Are The Symptoms of a Molar Pregnancy?

Because of the higher levels of human chorionic gonadotropin released by the growth in the uterus, many of the pregnancy symptoms in a molar pregnancy will seem amplified. In addition to amplified pregnancy symptoms of a molar pregnancy may include:

  • First trimester bleeding - dark brown to bright red vaginal bleeding
  • Intense nausea and vomiting
  • Passing grape-like cysts through the vagina

Other symptoms of a molar pregnancy may be detected by a doctor or health care professional and include:

  • Uterus too large for dates - signaling the rapid uterine growth of a molar pregnancy
  • Maternal hypertension
  • Preeclampsia - a dangerous condition that causes hypertension and protein in the urine after twenty weeks of pregnancy
  • Hyperthyroidism
  • Ovarian cysts
  • Anemia

How Is A Molar Pregnancy Diagnosed?

If a molar pregnancy is suspected, a physician may order the following:

Laboratory Blood Tests - to measure levels of hCG in the bloodstream of the mother.

Ultrasonography - depending upon dates of conception it may be an abdominal ultrasound or an internal ultrasound. The earlier in a pregnancy, the more likely it is that an internal ultrasound will be used. An ultrasound of a molar pregnancy may show:

  • No fetus or embryo
  • Ovarian cysts
  • Cystic placenta filling the uterus
  • No amniotic fluid 

In a partial molar pregnancy, an ultrasound may show:

  • Low amniotic fluid
  • Cystic, thick placenta
  • Growth-restricted fetus

How Is A Molar Pregnancy Treated?

A molar pregnancy cannot continue as it is not a normal or viable pregnancy. And prevention of complications includes removal of ALL molar tissue.

To remove the abnormal molar tissue, the doctor will order a D&C, which is done generally as an outpatient procedure under general anesthesia. The procedure should last up to a half an hour.

If the molar tissue in the uterus is severe and no future pregnancies are planned, the uterus may be removed to prevent future complications.

If a hysterectomy is not desired, the values of hCG must be carefully measured to ensure that they go down. If hCG levels do NOT go down, additional treatment may be necessary.

After the treatment for the molar pregnancy is complete, hCG levels will be monitored for up to a year to ensure that no molar tissue remains.

Pregnancy should be avoided for a full year following a molar pregnancy as the hCG values of a normal pregnancy can mask the rising hCG levels of growing molar tissue.

What Are The Complications of a Molar Pregnancy?

Even after a D&C is completed and the molar tissue is removed, some of the molar tissue may remain and begin to grow in a condition called "Gestational Trophoblastic Disease" (or GTD).

GTD occurs in about twenty percent of women who have been treated for a molar pregnancy (typically a full molar pregnancy rather than a partial molar pregnancy).

GTD may be diagnosed if levels of hCG continue to show up in the bloodstream even after the molar pregnancy has been removed. In certain cases, an invasive molar pregnancy penetrates into the middle layer of the uterus, which leads to vaginal bleeding.

Persistent GTD can almost always be treated successfully, often with chemotherapy and/or a hysterectomy.

Very rarely, a serious and cancerous complication of GTD called "choriocarcinoma" develops and spreads to other organs in the body. Choriocarcinoma is often successfully treated with a course of cancer drugs.

How To Cope With A Molar Pregnancy:

Losing a pregnancy - no matter the cause - is devastating. To go from thinking you're a happy pregnant lady to learning you have an invasive tumor, that can leave even the strongest of us weak in the knees.

Read more about how to cope with miscarriage.

After your molar pregnancy, you must remember to take care of yourself. It can be very hard as there are days in which you may not want to get out of bed. It's okay to grieve this loss.

Give yourself permission to grieve this loss. Do not push yourself to be better, work harder, and get over it. There's no simple solution to "getting over" something like a molar pregnancy.

Commemorate your pregnancy and your lost hopes in a tangible way. Plant a tree. Make a memory box. Anything you can to lessen the pain of losing a potential child.

Do not blame yourself. One of the worst (and most common) things that people do after a miscarriage is to find the reason - and blame themselves. This loss was not your fault.

Don't be afraid to tell others how you are feeling. Many people don't know how to comfort someone who is deeply grieving.

Write out your feelings - in a journal, for the Band, anything you can do to let it out.

If your feelings of grief are too intense for you to handle, don't hesitate to find a therapist trained in loss to help you through this difficult time.

And, be gentle on yourself. This is a trauma and a loss - allow yourself time to heal.

Related Resource Pages on Band Back Together:

How To Cope With Miscarriage


Recurrent Pregnancy Loss




Additional Molar Pregnancy Resources:

MolarPregnancy.co.uk - stories, treatments, and other information about molar pregnancies and the devastation they cause.

March of Dimes - information about ectopic and molar pregnancies from the March of Dimes.