Gestational Trophoblastic Disease
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Direct answer
A "snowstorm" ultrasound with a markedly raised beta-hCG, a uterus large for dates and painless first-trimester bleeding spells gestational trophoblastic disease (GTD) — complete mole (diffuse villous oedema, no fetus, usually 46XX of paternal origin) or partial mole (focal change, fetal parts present, triploid karyotype) — evacuated by suction catheter with histopathology to confirm. Post-molar surveillance is serial beta-hCG: weekly until normal for three weeks, then monthly for six months in standard protocols, with reliable contraception throughout, because a rising or plateauing titre means post-molar GTN needing chemotherapy. Choriocarcinoma may follow any pregnancy; low-risk postmolar GTN is treated with single-agent methotrexate or actinomycin-D with cure rates near 100 per cent, while the FIGO/WHO prognostic score of 7 or more defines high-risk disease demanding multiagent chemotherapy.
What you must remember
- Complete mole: all villi oedematous, no fetus, karyotype 46XX (paternal DNA duplication) in about 90 per cent; presents with passage of grape-like vesicles, uterus large for dates, hyperemesis, early pre-eclampsia (before 20 weeks) and hyperthyroidism from hCG cross-reactivity; theca-lutein cysts from ovarian hyperstimulation.
- Partial mole: focal villous swelling with fetal or fetal parts, triploidy (69XXY and similar), milder hCG rise, often mistaken clinically for miscarriage — diagnosed by histology after evacuation.
- Evacuation: suction evacuation is the method of choice; medical induction with oxytocin or prostaglandins is generally avoided (vesicle embolisation and dissemination concerns); hysterectomy is an option for older women finished with childbearing; anti-D if Rh negative.
- Follow-up protocol: weekly serum beta-hCG until negative for three consecutive weeks, then monthly for six months (commonly quoted FIGO schedule); contraception — combined pills traditionally after hCG normalises, or barrier/levonorgestrel methods earlier.
- Diagnosis of post-molar GTN: plateaued hCG (four values over three weeks), rising hCG (three values over two weeks), persistence beyond six months, histological choriocarcinoma, or metastases (lung, vagina, brain).
- FIGO/WHO prognostic score: age, antecedent pregnancy interval, pre-treatment hCG, tumour size and site, number of metastases and prior failed chemotherapy — 7 or more means high risk; FIGO anatomic stages I to IV.
- Chemotherapy: low-risk — single-agent methotrexate (with folinic acid) or actinomycin-D; high-risk — multiagent EMA-CO; metastases to lung and vagina respond well, brain and liver involvement is ominous.
Post-evacuation follow-up, month by month
Follow a 24-year-old after a complete mole is evacuated and confirmed on histology. Week zero: hCG is 220,000 IU/L; weekly values fall — 40,000, 6,000, 900 — and she is counselled that the first months decide everything, using barrier contraception meanwhile. Week four to six: the titre halves each week on schedule until negative; three consecutive negative weekly values close the first phase, and monthly testing continues for six months, because invasive mole and choriocarcinoma declare themselves as a plateau or rise in precisely this window.
Now rerun the timeline with a break: week six gives 1,400, week seven 1,450, week eight 1,390 — a plateau across three values. That is post-molar GTN by definition. Staging follows: pelvic ultrasound for an invasive uterine lesion, chest radiograph (cannonball metastases), and if lung lesions exist, brain imaging; blood count, liver and renal function, and the FIGO score is computed. A score of 3 places her low risk: single-agent methotrexate cycles with weekly hCG until negative, then consolidation cycles — and the counselling point FMGE wants is that she will almost certainly be cured and may bear children afterwards. A score of 9 with brain metastases sends her to a trophoblastic disease centre for EMA-CO with cranial irradiation or intrathecal therapy, where cure is still realistic in specialised hands.
What the exam repeats
Three questions recur. Which mole has fetal parts — partial, triploid. Which follow-up value triggers chemotherapy — the plateau or rise of serial hCG, with the exact plateau definition (four values within 10 per cent over three weeks) quoted in options. And why hyperthyroidism improves after evacuation — hCG shares its alpha subunit with TSH and stimulates the receptor, so the thyrotoxicosis of a mole is humoral, cured by the suction catheter, not by carbimazole. The pre-eclampsia-before-20-weeks vignette is the fourth: in a booking clinic it means "rule out molar pregnancy with ultrasound and hCG".
Frequently asked questions
How does a partial mole differ from a complete mole?
A partial mole has focal villous change with fetal parts and triploid karyotype with lower hCG; a complete mole has diffuse vesicular change, no fetus, and diploid paternal-origin karyotype with very high hCG.
What hCG follow-up is advised after molar evacuation?
Weekly serum beta-hCG until negative for three consecutive weeks, then monthly for six months, with reliable contraception to avoid a confusing pregnancy during surveillance.
What hCG pattern diagnoses post-molar trophoblastic neoplasia?
A plateau of four values over three weeks, a rise across three values over two weeks, persistence beyond six months, histological choriocarcinoma, or any metastasis.
Which chemotherapy is used for low-risk postmolar GTN?
Single-agent methotrexate with folinic acid rescue or actinomycin-D, with near-complete cure rates in low-risk disease.
Why does a molar pregnancy cause hyperthyroidism?
Extremely high hCG cross-stimulates the TSH receptor because the two share an alpha subunit; the thyrotoxicosis resolves after evacuation.