What is the recommended follow-up for a patient with a partial mole?

Follow-Up Protocol for Patients with Partial Mole

For patients with partial hydatidiform mole, serial hCG monitoring is required with weekly measurements until undetectable levels are achieved, followed by additional monitoring based on normalization timing. 1

Initial Management After Diagnosis

• Suction curettage is the preferred method for evacuation of partial molar pregnancy 1, 2
• Medical evacuation should not be used 2
• Anti-Rhesus D prophylaxis should be administered if the patient is Rh-negative 1
• Initial serum hCG should be measured at the time of evacuation 2

hCG Monitoring Protocol

For Triploid Partial Moles (>90% of cases)

• Measure serum hCG weekly until there are two consecutive undetectable values (<1 or <2 IU/L) 2
• After achieving undetectable levels, the patient can be discharged from follow-up 2

For Diploid Partial Moles or Those Without Valid Ploidy Determination

• Measure serum hCG weekly until the value is undetectable (<1 or <2 IU/L) 2
• If hCG becomes undetectable within 56 days after evacuation:
  • Continue with four additional monthly measurements 1, 2
• If hCG normalizes after 56 days:
  • Continue monthly measurements for 6 months 1, 2

Criteria for Persistent Trophoblastic Disease (PTD)

PTD is diagnosed if any of the following occur:

• hCG plateaus (less than 10% fall over three measurements)
• hCG increases
• hCG remains detectable for longer than 6 months 2

If PTD is diagnosed:

1. Obtain chest X-ray
2. Perform gynecologic ultrasound
3. Refer for oncologic treatment 2

Important Considerations

• Safe contraception should be used during the entire follow-up period 2
• The risk of persistent gestational trophoblastic neoplasia after partial mole is 0.5-5% 1
• Some studies suggest that a single undetectable hCG level after evacuation might be sufficient for follow-up in partial moles 3, but most guidelines recommend more extended monitoring
• Inadequate follow-up can lead to delayed diagnosis of persistent disease 1

Future Pregnancy Management

• In all subsequent pregnancies, offer an early ultrasound scan around gestational week 8 2
• Measure serum hCG eight weeks after termination of all future pregnancies 2
• The risk of a subsequent molar pregnancy after one molar pregnancy is approximately 1% 1

Potential Pitfalls

• Misdiagnosis of partial moles as complete moles or non-molar miscarriages can occur 1
• Some hCG assays may give false-positive or false-negative results; if results don't align with the clinical picture, measure hCG using a different assay 1
• Non-adherence to the monitoring protocol can lead to missed persistent disease (estimated risk of 1:2000 after completing the UK monitoring scheme) 1

By following this structured monitoring protocol, the risk of missing persistent gestational trophoblastic disease after partial molar pregnancy can be minimized while avoiding unnecessarily prolonged follow-up for most patients.