Molar Pregnancy

A hydatidiform mole, which is also called a "molar pregnancy," is a gestational trophoblastic disease (GTD) that starts in the placenta and can spread to other parts of the body. The tumor starts in fetal tissue instead of the tissue from the mother. Hydatidiform moles (HM) are usually thought of as the noninvasive form of gestational trophoblastic disease. They can be either complete or partial.

Last Updated: February 21, 2024

A molar pregnancy is found in about 1 out of every 1,000 pregnancies. Molar pregnancies have been linked to a number of risk factors. Women older than 35 or younger than 20 are more likely to have a molar pregnancy. A woman who has had a molar pregnancy is also more likely to have another one.

At first, a molar pregnancy may look like a normal pregnancy, but most molar pregnancies have certain signs and symptoms, such as:

  • Dark brown to bright red bleeding in the first three months of pregnancy;
  • Severe nausea and vomiting;
  • Presence of grape-shaped cysts that may sometimes pass through the vaginal canal;
  • Discomfort or pressure in the pelvis.

Other signs of a molar pregnancy include:

  • Rapid growth of the uterus—the uterus is too big for the stage of the pregnancy.
  • High blood pressure 
  • Preeclampsia (condition that happens after 20 weeks of pregnancy and causes high blood pressure and protein in the urine)
  • Ovarian cysts
  • Anemia
  • Hyperthyroidism

Serum hCG levels are usually much higher in people with hydatidiform moles than in people at the same stage of pregnancy who are having a normal pregnancy or an ectopic pregnancy. Serum hCG levels in complete moles are usually over 100,000, while levels in partial moles may be in the normal range for the gestational age. 

Some other tests done are:

    • CBC - to evaluate for anemia and thrombocytopenia;
    • Basic Metabolic Panel - to evaluate for electrolyte imbalances and renal insufficiency
    • Thyroid Panel - to check for signs and symptoms of hyperthyroidism;
  • Liver function test and urinalysis - to evaluate for transaminitis and proteinuria to rule out preeclampsia
  • Coagulation profile, including PT/INR - to check for disseminated intravascular coagulation in severe cases.

Treatment

Molar pregnancies cannot be continued as normal viable pregnancies. To avoid problems, the abnormal placental tissue needs to be taken out. Most treatments include at least one of the following steps:

  • Dilation and curettage (D&C). A procedure where doctors will remove the molar tissue from the uterus;
  • Hysterectomy. If there is a high risk of gestational trophoblastic neoplasia (GTN) and the woman does not want to get pregnant again, the uterus may be taken out;
  • After the molar pregnancy is removed, the hCG levels should be checked. If they stay high, this is a sign of a persistent or invasive disease that may need chemotherapy.

If a woman has had a molar pregnancy, doctor consultation or prenatal care is a must before trying to conceive again. It is advised to wait between six months and a year before trying to get pregnant. The chance of having another one is low, but it is higher than for women who have never had a molar pregnancy before.

A doctor may perform early ultrasounds in future pregnancies to check your status and reassure you. It may be recommended to do prenatal genetic testing to detect a molar pregnancy.

References

Ghassemzadeh S, Farci F, Kang M. Hydatidiform Mole. [Updated 2022 May 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459155/

Mayo Clinic (2022). Molar Pregnancy. Retrieved November 11, 2022, from https://www.mayoclinic.org/diseases-conditions/molar-pregnancy/symptoms-causes/syc-20375175

Last Updated: February 21, 2024