What is molar pregnancy?

Molar pregnancy, which also goes by the name “hydatidiform mole” is a gestational trophoblastic disease (GTD). Trophoblasts are the first cells to develop once an egg is fertilized. They supply the embryo with nutrients and become part of the placenta. In a healthy pregnancy, this process is well controlled by the body. But in GTD, the body’s regulatory systems are not working properly. This leads to the proliferation of abnormal tissue that resembles clusters of grapes. The molar growth must be removed because it has the potential to develop into a choriocarcinoma, which is a rapidly metastasizing malignancy.

Hydatidiform moles vary in composition and can be complete or partial moles. In a normal pregnancy, the embryo gets one set of chromosomes from each parent, for a total of 46 chromosomes. Hydatidiform moles can be complete or partial and each type has chromosomal abnormalities.

Complete mole

The complete hydatidiform mole has no chromosomes from the egg and 23 chromosomes from sperm. This occurs when an egg with no nucleus is fertilized by either a single sperm or by two sperm. In a complete mole, the egg is empty and no fetus develops.

  • Chromosomes: 23 from one sperm (most common) or two sperm (about 20% of cases)
  • hCG: Greater than 100,000 mlU/mL
  • Fetus: Absent
  • Fetal parts: None
  • Placenta: Present but abnormal
  • DNA: Only paternal DNA is expressed
Complete Molar Pregnancy

Partial mole

The partial hydatidiform mole occurs when an egg with maternal DNA is fertilized by two sperm. In this case there is an excess of genetic material. Many partial moles are misdiagnosed as spontaneous abortions (miscarriage) and are only discovered after the tissue is examined.

  • Chromosomes: 23 from egg, 46 from two sperm (23 chromosomes in each sperm)
  • hCG: May be normal or lower than normal
  • Fetus: May be present
  • Fetal parts: May be present
  • Placenta: Present but abnormal
  • DNA: Maternal and paternal DNA is expressed
Partial Molar Pregnancy

Who is most at risk for molar pregnancy?

Individuals at higher risk are those with previous molar pregnancy, adolescent pregnancy, advanced maternal age (over 40), smoking, previous infertility issues or spontaneous abortions, and a diet deficient in beta carotene (Vitamin A).

What are the complications of molar pregnancy?

One of the key complications of molar pregnancy is the progression to gestational trophoblastic neoplasia (GTN), which includes choriocarcinoma, epithelioid trophoblastic tumor and invasive mole. These malignancies metastasize and may be fatal if not treated. The main treatment for malignancies of this type is chemotherapy, but some individuals may also require a hysterectomy, radiation, or a combination of therapies.

Note that GTD can occur in cases of multiple gestation where there is a fetus and complete or partial mole in the same pregnancy. This requires very careful prenatal management in order to have a live birth of the fetus.

Other complications include: 

  • Infection, that can progress to sepsis and shock
  • Preeclampsia
  • Hyperemesis leading to dehydration and malnourishment
  • Severe bleeding
  • Thyroid storm (hyperthyroidism occurs in about 7 to 10% of cases)
  • Pulmonary edema (rare but can occur)

Now that you’ve got some background information on molar pregnancy, let’s learn how to care for these patients using the Straight A Nursing LATTE method.


L: How does the patient LOOK? 

The common signs/symptoms of molar pregnancy include: 

  • Vaginal bleeding that may appear dark or “prune-juice” colored
  • Passage of tissue that resemble clusters of grapes
  • Enlarged uterus
  • Pelvic pressure or pain (often due to the enlarged uterus but can also be due to the presence of ovarian cysts in complete molar pregnancy)
  • Hyperemesis gravidarum (due to high levels of hCG)

Less common symptoms include:

  • Hyperthyroidism (hCG is believed to stimulate the thyroid)
  • Early onset preeclampsia (occurring before 20 weeks)

A: How do you ASSESS the patient?

  • Measure fundal height
  • Monitor I/O if vomiting is persistent
  • Monitor for signs of bleeding
  • Assess patient for signs of hyperthyroidism such as tachycardia, tremors, anxiety, increased appetite, sweating.
  • Measure blood pressure

T: What TESTS will be ordered for a patient with suspected or confirmed molar pregnancy?

  • hCG – The key blood test for molar pregnancy is hCG (serum human chorionic gonadotropin). In a complete molar pregnancy, hCG is abnormally high and often exceeds 100,000 mIU/mL. 
  • Transvaginal ultrasound – A transvaginal ultrasound is utilized when molar pregnancy is suspected, though it may be inconclusive and misdiagnosed as an incomplete abortion.
    • Complete mole on transvaginal ultrasound:
      • No embryo or fetus
      • No amniotic fluid
      • Placenta is markedly abnormal with enlarged cystic spaces (sometimes called “swiss-cheese” appearance)
      • Presence of ovarian cysts due to elevated hCG levels
    • Partial mole on transvaginal ultrasound:
      • Fetus or fetal parts may be seen
      • Amniotic fluid present, may be low
      • Swiss cheese appearance of placenta
      • Enlarged gestational sac
  • CT Scan and PET scan may be utilized to further evaluate and stage the GTD.
  • Additional blood tests may be conducted depending on the individual’s clinical presentation and may include CBC, renal panel, urine protein, liver enzymes, and thyroid panel.
  • Uterine evacuation – Once the uterus is evacuated, confirmation of molar pregnancy is possible with examination of the abnormal tissue. 

After uterine evacuation, hCG levels are monitored regularly until they return to undetectable levels. If the hCG level does not normalize in the post-operative period, this is suggestive for GTN and the patient may need chemotherapy.

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T: What TREATMENTS are utilized for molar pregnancy?

The main treatment for molar pregnancy is evacuation of uterine contents. This can be done as an outpatient procedure or under anesthesia. The procedure involves dilation of the cervix, suction aspiration and sharp curettage to ensure all the abnormal tissue is removed.

Hysterectomy may be indicated in some patients, such as those over the age of 40 or for an individual who does not wish to have additional pregnancies. One benefit of hysterectomy is it reduces the risk of GTN.

Of course, treatments will be utilized based on individual complications such as preeclampsia, bleeding or hyperthyroidism.

E: How do you EDUCATE the patient?

Key teaching for a patient who has had a molar pregnancy includes:

  • Since the patient is at higher risk for molar pregnancy in the future, they should know what signs and symptoms to watch for and to see their physician when they suspect they are pregnant.
  • Teach the patient the importance of follow-up hCG measurements and that they are necessary to evaluate if the molar pregnancy has progressed to GTN.
  • Ensure the patient understands to use a reliable method of birth control while undergoing serial hCG testing since a pregnancy makes it impossible to properly interpret the hCG levels.
  • After a D&C (uterine evacuation), teach the patient that light bleeding is expected. If they notice heavy bleeding, they should notify their physician. 
  • Teach the patient to avoid using tampons or engaging in sexual intercourse until healing from the D&C is complete.
  • Teach the patient to notify their physician if they experience fever, persistent or increasing pain, or foul-smelling discharge (essentially signs of infection).

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