Pregnancy health

What is a molar pregnancy?

Read on to learn more about the symptoms, treatment options and complications of this rare and heartbreaking condition.

What is a molar pregnancy?

Photo: iStockphoto

Many of us haven’t heard of a molar pregnancy, a rare condition that happens in about one in 1,000 pregnancies. Also known as a hydatidiform mole, a molar pregnancy can take a couple of different forms and, sadly, neither of them is a pregnancy that can continue.

What is a molar pregnancy?

There are two kinds of molar pregnancy. In a complete molar pregnancy, a fetus doesn’t develop. Instead, a single sperm fertilizes an abnormal, empty egg with no genetic information, so all of the genetic information comes from the father. The fertilized egg grows into a lump of tissue that looks like a cluster of grapes in the uterus. In a partial molar pregnancy, an egg is fertilized by two sperm, so there is an extra set of the father’s chromosomes. A fetus may start to form, but it isn’t able to survive.

Why do molar pregnancies happen?

Most molar pregnancies are sporadic, which means that they happen for no reason at all and are not linked to genetics. Risk factors include age (if you are younger than 20 or older than 35, a molar pregnancy is more likely to occur) and medical history (if you have more than one molar pregnancy, you will likely be referred to a genetic counsellor for testing).

What are the symptoms of a molar pregnancy?

Symptoms may include bright red to dark brown vaginal bleeding during the first trimester, pelvic pressure or pain, the passing of grapelike cysts from the vagina, and severe nausea and vomiting.

How is a molar pregnancy treated?

“Typically, a diagnosis is made with a combination of an ultrasound and a serum quantitative human chorionic gonadotropin [hCG] blood test,” says Lua Eiriksson, a gynaecologic oncologist in Hamilton, Ontario. “The ultrasound will show an abnormal pregnancy, and the hCG test will usually show that this pregnancy-related hormone is higher than what you would expect at this point in the pregnancy.” The patient would be referred to a gynaecologist, and the most likely treatment option is dilation and curettage (D&C), a day-surgery procedure done under local or general anaesthetic where abnormal tissue in the uterus is removed. The tissue removed is sent to pathology to confirm the diagnosis, and weekly bloodwork is done to monitor hCG levels. “It’s expected that, once the uterus is evacuated, the hCG levels will decrease until they’re undetectable,” says Eiriksson. This usually takes about six months.

Are there potential complications?

If blood work shows that hCG levels aren’t going down, then the diagnosis changes to an “invasive mole,” which means that molar tissue remains in the body and continues to grow. It happens in up to five percent of partial molar pregnancies and about 15 to 20 percent of complete molar pregnancies. This is called persistent gestational trophoblastic neoplasia (GTN), and it can be treated with a second surgery to remove the tissue again. However, if the cells keep growing, it’s considered cancer (yes, this is scary). “The vast majority of these patients have a curable disease,” says Eiriksson. “If you are low risk, it can be treated with a single round of chemotherapy and be cured.”


Understandably, a molar pregnancy is a sad, stressful experience. Natalie Stechyson of Ottawa recently had a molar pregnancy and wrote about her experience in HuffPost Canada. She says it felt like a “never-ending miscarriage” because of her complications and the need for eight months of procedures and blood work to see if things were getting worse instead of better. Stechyson needed a second D&C to completely remove the tissue and, fortunately, her hCG levels are now normal. “I knew the cancer risk was very, very low, but I still went to some dark and scary places,” she says. “Looking back, I realize that I needed to process the fact that I had lost a pregnancy. You can’t dismiss this just because it wasn’t a typical pregnancy.” Stechyson found that one of the most helpful ways to cope was through a Facebook support group run by “I didn’t feel so alone,” she says, “and it was a place to get good information from women who were going through the same thing and be understood.”

Can you get pregnant again?

The vast majority of women who experience molar pregnancies will be able to conceive and deliver healthy babies if they want to get pregnant again,” says Eiriksson. “Usually, a molar pregnancy is sporadic, and it’s not likely to happen again.”

This article was originally published on Jan 11, 2020

Weekly Newsletter

Keep up with your baby's development, get the latest parenting content and receive special offers from our partners

I understand that I may withdraw my consent at any time.