Key Points
A molar pregnancy is a non-cancerous tumor that develops in the uterus at the beginning of pregnancy.
If not treated, a molar pregnancy can be dangerous to a woman. It almost always ends in pregnancy loss.
Call your provider right away if you have bleeding from the vagina or intense nausea and throwing up. These can be signs and symptoms of a molar pregnancy.
What is a molar pregnancy?
A molar pregnancy (also called a hydatidiform mole or HM) is a tumor (growth) that develops in the uterus (womb) at the beginning of pregnancy. It happens when the egg and sperm don't join correctly, causing a growth that looks like small, fluid-filled sacs, similar to a bunch of grapes. This growth can't support a baby, so the pregnancy ends. Sometimes a miscarriage occurs, but if not, surgery is needed to remove it. If not treated, a molar pregnancy can lead to serious health problems.
What causes a molar pregnancy?
Molar pregnancy is caused when there’s a problem with an embryo’s chromosomes. Chromosomes are the structures that hold genes. For each pair of chromosomes, you get one from your mother and one from your father, so you have 46 in all. Molar pregnancy happens when there are two sets of chromosomes from the father.
There are two kinds of molar pregnancy:
- Complete molar pregnancy. In this condition, there’s no embryo or placental tissue. It happens when chromosomes from the mother’s egg are missing or not working, and chromosomes from the father are copied, so all 46 chromosomes come from the father.
- Partial molar pregnancy. In this condition, the mother's chromosomes are present, but the father provides two sets of chromosomes, giving the embryo 69 chromosomes instead of 46. This usually happens when two sperm fertilize the egg, leading to an extra set of chromosomes from the father.
Are you at risk for having a molar pregnancy?
You may be more likely than other women to have a molar pregnancy if you:
- Are younger than 20 or older than 40.
- Have had a molar pregnancy before
- You’ve had two or more miscarriages
What are the signs and symptoms of a molar pregnancy?
A molar pregnancy may seem like a healthy pregnancy at first. But call your health care provider right away if you have any of these signs or symptoms:
- Bleeding from the vagina in the first 3 months of pregnancy
- Grape-like cysts that come from your vagina. A cyst is a sac filled with fluid.
- Intense nausea and throwing up. Nausea is feeling sick to your stomach.
- Pelvic pressure or pain. This happens rarely.
When checking your health, your provider may find other signs of a molar pregnancy, including:
- Anemia
- Cysts on your ovaries.
- High blood pressure (also called hypertension).
- Hypothyroidism.
- Your uterus grows too much or too little.
How is a molar pregnancy diagnosed?
Your provider uses ultrasound to diagnose a molar pregnancy. Your provider also gives you a blood test to measure the levels of a pregnancy hormone called human chorionic gonadotropin (also called hCG). A molar pregnancy can cause hCG levels to rise more slowly than in a healthy pregnancy.
How is a molar pregnancy treated?
If you have a molar pregnancy, your provider does a procedure called dilation and curettage (also called D&C) to remove the molar tissue (tissue from the tumor) from the lining of your uterus. After your procedure, your provider regularly measures your hCG levels until they’re normal. Your provider may want to check your hCG levels for 6 months to 1 year to be sure there’s no molar tissue in your uterus. Your provider may recommend that you not get pregnant during this time. Being pregnant changes your hCG levels and makes it hard to detect molar tissue.
If tissue still grows in the uterus after a D&C molar, it can cause a condition called persistent GTD. Persistent GTD can be treated with hysterectomy or chemotherapy. A hysterectomy is surgery to remove your uterus. Chemotherapy is medicine used to treat cancer. In rare cases, you may get a cancer-causing form of GTD called choriocarcinoma. This condition is treated with several kinds of cancer medicines.
More information
From hurt to healing (free booklet from the March of Dimes for grieving parents)
Share Your Story (March of Dimes online community for families to share experiences with prematurity, birth defects or loss)
Centering Corporation (general grief information and resources)
Share Pregnancy & Infant Loss Support (resources for families with pregnancy or infant loss)
Last reviewed: October, 2024