The incidence varies widely in different parts of the world. The disease incidence is influenced by socio-economic and nutritional factors. Maternal age, prior spontaneous miscarriage and infertility have all been shown to increase the risk of a molar gestation. In the USA, the incidence is 1/1500 livebirths.

Clinical features

• Vaginal bleeding: this could be significant and prolonged, leading to significant anemia. The patient may occasionally experience the passage of the pathognomonic grape-like vesicles.
  
• Uterine size larger than gestational age: it is important to rule out other causes of an enlarged uterus, such as multiple gestations, leiomyomas, and polyhydramnios.
  
• Toxemia: this is classically associated with hypertension, proteinuria, and hyper-reflexia. When it happens in early pregnancy, GTN should be ruled out as the underlying cause.
  
• Hyperemesis: this can occasionally be severe enough to require treatment with intravenous fluid. This is more likely to happen in patients with markedly elevated levels of hCG.
  
• Hyperthyroidism: this can be associated with its classic signs of tachycardia, tremor and warm skin.
  
• Theca lutein ovarian cysts: these are related to the elevated levels of hCG. They do not require surgical intervention and resolve spontaneously after the successful treatment of the GTN.

Imaging studies

Ultrasound remains a sensitive modality for diagnosing molar pregnancy. Due to its widespread use, molar pregnancies are being diagnosed earlier and earlier. This will help rule out multiple gestations, confirm the large uterine size and document the presence of the theca lutein ovarian cysts. The characteristic vesicular sonographic pattern is known as the “snowstorm.”

Laboratory work-up

• Serum hCG: markedly elevated levels of serum hCG are suggestive of complete hydatidiform mole. However, patients with partial hydatidiform mole are less likely to present with very high levels of hCG. Patients with placental site trophoblastic disease can actually have a normal hCG level.
  
• Urine hCG: in the past, the measurement of urinary hCG was used to help identify patients with molar pregnancies. Its current use is limited to evaluating cases with “false-positive” or “phantom” serum hCG. This is caused by a circulating heterophilic antibody that can produce a false elevation in serum hCG. Therefore, serum and urine samples should be collected simultaneously. Patients with “phantom” hCG will have no measurable hCG in their urine sample.
  
• Thyroid function test: elevated serum levels of free thyroxine (T4) and tri-iodothyronine (T3) can commonly be detected in asymptomatic patients with hydatidiform mole. These levels will rapidly normalize after the evacuation of the molar gestation.
  
• Type and screen: after the evacuation of the molar gestation, it is recommended that RhoGAM be given to Rh-negative mothers, although hydatidiform mole has not been documented as a cause of Rh sensitization.

Tissue diagnosis

The pathologic examination of the evacuated tissue remains an important part of the diagnosis. This will help differentiate between the different entities of complete, partial or invasive mole and rule out choriocarcinoma or placental site trophoblastic disease.

As soon as the diagnosis of molar gestation is confirmed, the patient should be evaluated for the presence of complications including anemia, electrolyte imbalance, hyperthyroidism and pre-eclampsia. Once she is stabilized, the route of evacuation should be decided. The desire for future fertility is an important factor in making this decision.

Evacuation-termination

The molar pregnancy should be evacuated by suction curettage. This remains the preferred method when fertility preservation is desired. Conventional sharp curettage is adequate in patients who have spontaneously evacuated part of the mole so that the uterus is less than 12 weeks’ gestational size. Oxytocin or prostaglandin induction is indicated only in the patient with a co-existent fetus. Suction curettage is carried out under general anesthesia in the operating room. If the patient is bleeding heavily on admission, an oxytocin infusion is started at the time; otherwise, none is given until the curettage is under way or completed.

Hysterectomy