A molar pregnancy is a rare pregnancy complication that happens when abnormal tissue — instead of a healthy placenta — grows inside the uterus. It occurs because of a problem during fertilization and isn't a viable pregnancy. While the diagnosis can be heartbreaking, early treatment is highly effective, and most women go on to have healthy pregnancies at a later time.
Learn more about why molar pregnancies happen, what symptoms they can cause, and how they're treated.
What is a molar pregnancy?
A molar pregnancy (also called a hydatidiform mole) happens when the tissue that’s meant to become the placenta overgrows, forming a mass of cysts. There are two types of molar pregnancies:
- A complete molar pregnancy means there's no embryo or placental tissue.
- A partial molar pregnancy means there is some identifiable embryonic or fetal tissue.
Most molar pregnancies are discovered within weeks of conception, and unfortunately all end in miscarriage.
What causes a molar pregnancy?
A molar pregnancy is caused by a genetic abnormality during fertilization. Usually a fertilized egg contains one set of 23 chromosomes from the father and one set of 23 chromosomes from the mother. A partial mole happens when there are two sets of chromosomes from the father and one set of chromosomes from the mother. A complete mole happens when there are two sets of chromosomes from the father and none from the mother.
"I just found out at 13 weeks that I have a molar pregnancy," says What to Expect Community member rachelkate08. "I'm pregnant but not pregnant ... It's a miscarriage without actually miscarrying ... I really don't know how to feel."
How common are molar pregnancies?
Molar pregnancies are relatively rare, occurring only in about 1 out of every 1,000 pregnancies.[1]
Who is most at risk of having a molar pregnancy?
Women who are at slightly increased risk for a molar pregnancy include those who:
- Are over age 35
- Are under age 20
- Have had multiple miscarriages
Get more expert advice and connect with other moms facing similar challenges on our free What to Expect app.
What are the symptoms of a molar pregnancy?
The most common symptom of a molar pregnancy is continuous or intermittent brown or bright red vaginal bleeding or bloody discharge. Other symptoms can include:
- Severe nausea and vomiting
- Unusual or severe cramping
- Unexplained weight loss
- High blood pressure
- A uterus that's larger than expected for gestational age
- A soft or "doughy" uterus (rather than firm)
- Absence of embryonic or fetal tissue (seen on ultrasound)
- Excessively high thyroid hormone levels
- Passage of one or more oval-shaped, grape-like cysts (called a trophoblasts) from the vagina
- Ovarian cysts (detected by your practitioner)
- Preeclampsia (usually diagnosed by your practitioner)
What should I do if I think I'm experiencing a molar pregnancy?
Call your practitioner if you experience any of the symptoms listed above. Since some of these symptoms can be difficult to distinguish from normal early pregnancy symptoms, trust your instincts. Many healthy pregnancies include some spotting and cramping, and most include nausea. If you think something isn't right, contact your practitioner — even if only for reassurance.
"I previously had a molar pregnancy, a complete molar," says Community mom laurenw206. "I had absolutely no symptoms whatsoever, just a feeling something was wrong. I had it confirmed at an ultrasound at 8 weeks and had a D&C a couple of days later."
How is a molar pregnancy treated?
Your practitioner will likely perform an ultrasound and blood tests (to measure hCG levels). They may also recommend a chest X-ray or MRI of your abdomen.
If you do have a molar pregnancy, the abnormal tissue must be removed through a dilation and curettage (D&C), a procedure that usually takes 15 to 30 minutes. Your practitioner will use a speculum (the same tool used during a routine pelvic exam) to view and dilate your cervix before removing the tissue.[2]
Follow-up testing to monitor your hCG levels is crucial to make sure that abnormal tissue doesn’t continue to grow or progress to choriocarcinoma. Luckily, the risk of a treated molar pregnancy becoming malignant is extremely rare.
Should I be concerned if I think I've had a molar pregnancy?
Usually, there's no reason to be concerned as long as you've received proper medical care for your molar pregnancy.
A molar pregnancy is a risk factor for developing persistent gestational trophoblastic neoplasia (GTN). Also known as gestational trophoblastic disease, this condition occurs when placental tissue left behind after treatment continue to grow.[3]
Very rarely, this can lead to a form of cancer known as choriocarcinoma. Both GTN and choriocarcinoma are extremely uncommon, with choriocarcinoma occurring in only about 1 out of every 40,000 pregnancies.
How soon can I get pregnant again after a molar pregnancy?
Your practitioner will probably recommend waiting about 6 to 12 months after a molar pregnancy before trying to conceive again.
"It was extremely hard being told that we lost our first baby and that we had to wait before trying again," says Community member mmhale3. "At the time, getting pregnant again felt like the only thing that would make me feel better."
The good news is that having one molar pregnancy usually doesn't significantly increase your risk of another. Only 1% to 2% of women who have had one molar pregnancy go on to experience a second one.
"I had a molar pregnancy when I was 18," says Community mom Cawasartn. "It was hard and scary. I have had six babies since."
Yes 
No 
