Gynecology Topic 46. Hydatidiform mole

I. Definition and Classification

Definition

• Hydatidiform mole / molar pregnancy: Benign gestational trophoblastic disease with abnormal trophoblastic proliferation and hydropic swelling of chorionic villi.
• It is usually confined to the uterus but may persist as gestational trophoblastic neoplasia (GTN): invasive mole or choriocarcinoma.
• Risk factors: Previous molar pregnancy and extremes of reproductive age.

Complete Mole

• Genetics: Empty ovum fertilized by one sperm that duplicates or by two sperms.
• Karyotype: Usually 46,XX; less often 46,XY; only paternal nuclear chromosomes.
• Histology: Diffuse hydropic villi + diffuse trophoblastic proliferation.
• No fetal tissue or fetal vessels.
• β-hCG often very high, commonly >100,000 IU/L.
• Malignant/persistent potential: Higher; postmolar GTN about 15-20%, may transform to choriocarcinoma.

Partial Mole

• Genetics: Normal ovum fertilized by two sperms or duplicated paternal set.
• Karyotype: Triploid, usually 69,XXY; also 69,XXX or 69,XYY.
• Histology: Some hydropic villi + focal trophoblastic proliferation.
• Abnormal fetus/fetal parts may be present; fetus is usually nonviable.
• β-hCG increased but usually less extreme than complete mole.
• Malignant/persistent potential: Lower, usually <5%.

II. Clinical Features and Complications

Clinical Features

• Amenorrhea and positive pregnancy test.
• Vaginal bleeding: Usually 1st or early 2nd trimester.
• Passage of grape-like vesicles: Classic but uncommon.
• Uterus larger than gestational age / size-date discrepancy, especially complete mole.
• Absence of fetal movement/heart sounds when expected.
• Excessive nausea/vomiting due to high hCG.
• Theca-lutein cysts: Bilateral ovarian cysts due to hCG stimulation; usually regress after evacuation.

Complications

• Hemorrhage and anemia.
• Infection.
• Trophoblastic embolization → Respiratory distress rarely.
• Preeclampsia before 20 weeks.
• Hyperthyroidism/thyrotoxicosis: hCG cross-reacts with TSH receptor.
• Persistent GTN: Invasive mole or choriocarcinoma.

III. Diagnosis

Clinical, Laboratory and Ultrasound

• Physical examination: Enlarged uterus, open cervix, grape-like vesicles in vagina/cervix if present.
• Quantitative serum β-hCG: Markedly increased; >100,000 IU/L strongly supports complete mole in the right context.
• Baseline tests: CBC, blood group/Rh, liver/renal tests; thyroid tests if symptomatic or hCG very high.
• Transvaginal ultrasound:

• Complete mole: Snowstorm / cluster-of-grapes pattern, no fetus.
• Partial mole: Thick/cystic placenta, focal molar change, fetal parts may be seen.
• Theca-lutein cysts may be seen in the ovaries.

• Histopathology of evacuated tissue is definitive.
• Chest X-ray: Baseline screen for lung metastasis if GTN suspected or per local protocol.

IV. Treatment

Evacuation

• Gold standard: Suction evacuation / suction curettage of uterine cavity.
• Send all tissue for histopathology.
• Large uterus/high-risk case: Ensure IV access, blood availability and anesthesia planning.
• Oxytocin: Give after evacuation has begun or after most tissue is removed to induce uterine contraction and reduce blood loss.
• Avoid vigorous uterotonics before evacuation when possible because contractions may increase trophoblastic embolization risk.
• Hysterectomy: Option if no future fertility desired or uncontrollable bleeding/coexisting uterine disease; hCG follow-up is still required.

Follow-Up

• Monitor quantitative serum β-hCG after evacuation until normal/undetectable.
• Classic exam schedule: Weekly until normal for 3 consecutive weeks, then monthly surveillance according to local GTD protocol.
• Effective contraception during monitoring, commonly OCP, prevents pregnancy-related hCG rise confusing follow-up.
• Pelvic ultrasound if retained tissue, uterine abnormality or persistent hCG is suspected.

Persistent Trophoblastic Disease

• Suspect persistent GTN if β-hCG plateaus, rises, remains detectable too long, or metastasis appears.
• Persistent disease after evacuation may be invasive mole or choriocarcinoma.
• Low-risk persistent GTN: Single-agent chemotherapy, commonly methotrexate or actinomycin D depending on protocol.
• High-risk/metastatic GTN: Multi-agent chemotherapy in a specialist GTD center.
• Future pregnancy is usually possible after completed surveillance and remission; next pregnancy needs early ultrasound.