Molar pregnancy

A molar pregnancy — also known as hydatidiform mole — is a noncancerous (benign) tumor that develops in the uterus. A molar pregnancy starts when an egg is fertilized, but instead of a normal, viable pregnancy resulting, the placenta develops into an abnormal mass of cysts.

In a complete molar pregnancy, there's no embryo or normal placental tissue. In a partial molar pregnancy, there's an abnormal embryo and possibly some normal placental tissue. The embryo begins to develop but is malformed and can't survive.

A molar pregnancy can have serious complications — including a rare form of cancer — and requires early treatment.

Symptoms Causes Risk factors Complications Prevention

A molar pregnancy may seem like a normal pregnancy at first, but most molar pregnancies cause specific signs and symptoms, including:

  • Dark brown to bright red vaginal bleeding during the first trimester
  • Severe nausea and vomiting
  • Sometimes vaginal passage of grape-like cysts
  • Rarely pelvic pressure or pain

If you experience any signs or symptoms of a molar pregnancy, consult your doctor or pregnancy care provider. He or she may detect other signs of a molar pregnancy, such as:

  • Rapid uterine growth — the uterus is too large for the stage of pregnancy
  • High blood pressure
  • Preeclampsia — a condition that causes high blood pressure and protein in the urine after 20 weeks of pregnancy
  • Ovarian cysts
  • Anemia
  • Overactive thyroid (hyperthyroidism)

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