What Is a Molar Pregnancy?

Molar PregnancyA molar pregnancy results from a genetic anomaly during fertilization. In a molar pregnancy, the placenta develops into an abnormal fast-growing mass of cysts. Molar pregnancies are also called gestational trophoblastic disease (GTD) or hydatidiform mole, whereby mole refers to the mass of tissue that is growing. In a partial molar pregnancy, there is an abnormal embryo and occasionally some normal placental tissue and the embryo fails to survive. In a complete molar pregnancy, there is no embryo or normal placental tissue. Due to being associated with serious complications, such as developing into a rare form of cancer, molar pregnancies require early treatment.


A molar pregnancy begins as any other pregnancy – a positive line on a pregnancy test and a missed period. However, usually you will start experiencing some symptoms that aren’t part of a normal pregnancy, such as:

  • Bright red to dark brown bleeding during the first trimester
  • Severe nausea and/or vomiting
  • Vaginal passage of grape-like cysts
  • Pelvic pain or pressure (rarely)

As well as symptoms that you can detect yourself at home, your doctor will also be able to detect other signs of a molar pregnancy. These include:

  • High human chorionic gonadotropin (hCG) levels
  • Uterine growth that is too fast for your stage of pregnancy
  • High blood pressure
  • Preeclampsia
  • Ovarian cysts
  • Overactive thyroid

Risk factors

Women who are younger than 20 years of age or older than 40 years of age are more at risk of developing a molar pregnancy. Other risk factors include:

  • Diet low in protein, carotene, or folic acid
  • History of miscarriage
  • Caucasian ethnicity (in the USA)
  • Previous molar pregnancy

Luckily molar pregnancies are relatively rare, affecting only one in 1000 pregnancies.


Molar pregnancies should be removed as soon as possible upon diagnosis with either a surgical procedure (uterine suction or surgical curettage) or medication.

If the molar pregnancy is considered to be invasive then a type of chemotherapy is given called methotrexate. However, this is administered at a low dose and consequently does not have the typical side effects normally associated with chemotherapy.

Following each of these treatments, you will be followed regularly to make sure that your hCG levels are decreasing. You will also be advised not to conceive for at least 6 months to a year following treatment.


Sometimes not all of the tissue is removed following treatment and the tissue that remains can continue to grow – this is called persistent GTD and it occurs in around 1 out of every 5 women who experience a molar pregnancy. The main sign of persistent GTD is hCG levels that continue to rise after treatment.

Occasionally, molar pregnancies can develop into an aggressive type of cancer called choriocarcinoma; however, this cancer is very treatable and almost all patients are cured following treatment with chemotherapy.

Dealing with the aftermath of a molar pregnancy

Although removing a molar pregnancy is different to the termination of a developing healthy embryo, it is still a significant loss, especially if the pregnancy was very much wanted. In addition, not only do you have to deal with your dreams and hopes of a baby suddenly being canceled, you may experience stress due to the potentially serious health risks that can develop from a molar pregnancy.

Allow yourself and your partner time to grieve. People may try to console you with comments such as ‘at least it wasn’t a proper baby’ and although this may seem harsh, they are only trying to help and are probably struggling for something appropriate to say.

Melody Watson
Melody Watson holds Bachelors degrees in Biochemistry and Microbiology. She works as a medical writer for a medical communications agency in Berlin, Germany, where her work ranges from medical translation to writing publications for medical journals. Melody is passionate about promoting science, including evidence-based medicine, and debunking pseudoscience.

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