Gestational Trophoblastic Disease (Post-evacuation Surveillance)
A 44-year-old woman underwent suction evacuation of a partial hydatidiform mole, confirmed on histopathology. Two weeks later she has no vaginal bleeding, blood pressure is 120/76 mm Hg, hemoglobin is 118 g/L, and serum beta-hCG has fallen from 90,000 to 4,000 IU/L. She asks about surveillance. Which of the following is the most appropriate follow-up plan?
- A.Monthly serum beta-hCG measurement
- B.Weekly pelvic ultrasound scan
- C.Weekly serum beta-hCG measurementCorrect
- D.Monthly pelvic ultrasound scan
Explanation
After evacuation of any molar pregnancy, surveillance is with weekly serum beta-hCG until the level is undetectable on three consecutive weekly samples, followed by monthly measurements for up to 6 months. Beta-hCG is the ideal marker because it is produced only by trophoblast, so any residual or invasive disease is reflected directly in the level. A plateau across four values, a rise of 10 percent or more across three values, or persistence beyond 6 months defines gestational trophoblastic neoplasia and prompts staging and chemotherapy, usually single-agent methotrexate or actinomycin D. Weekly rather than monthly sampling is essential in the early phase, because a plateau or rise must be caught before disease burden grows. Reliable contraception, typically combined oral contraceptives, is advised throughout follow-up so that a new pregnancy does not confound the interpretation of a rising hCG. Ultrasound cannot detect microscopic persistent trophoblast and is used only for initial diagnosis or when local uterine invasion is suspected, so neither weekly nor monthly scanning is the standard. The risk of neoplasia after a partial mole is lower than after a complete mole, roughly 1 to 5 percent, but surveillance is still mandatory.
Why each option
- A.
- Monthly testing is the later phase of surveillance, used after beta-hCG has been undetectable for three consecutive weeks. Starting monthly would delay detection of a plateau or rise.
- B.
- Ultrasound cannot detect microscopic persistent trophoblastic tissue and is not the surveillance modality for gestational trophoblastic neoplasia.
- C.
- Correct. Weekly beta-hCG until undetectable on three consecutive samples, then monthly for up to 6 months, is the standard post-evacuation protocol with contraception throughout.
- D.
- Monthly scanning is even less sensitive than weekly scanning and still cannot detect microscopic disease; beta-hCG is the marker of choice.
Reference: UpToDate 2025, Hydatidiform mole: Treatment and follow-up
This is one of 3,306 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank