Molar Pregnancy Summary

Overview

  • Abnormal conception with excessive placental development
  • Incidence: 1-3 per 1000 pregnancies
  • 10% progress to malignant GTN
  • Higher risk at reproductive age extremes

Types

  • Complete mole: No fetal tissue, diffuse hydropic changes
  • Partial mole: Fetal tissue present, focal changes
  • GTN: Malignant transformation

Clinical Features

  • Irregular vaginal bleeding + positive pregnancy test
  • Ultrasound findings characteristic
  • Hyperemesis, excessive uterine enlargement
  • Hyperthyroidism, early pre-eclampsia

Diagnosis

  • Ultrasound findings suggestive
  • Histological confirmation required
  • All products of conception must be sent for pathology
  • hCG monitoring essential

Management

  • Suction curettage (method of choice)
  • Anti-D prophylaxis post-evacuation
  • hCG monitoring for 6-12 months
  • Chemotherapy for GTN

Follow-up

  • Weekly hCG until normal x3
  • Monthly hCG for 6-12 months
  • Avoid pregnancy during monitoring
  • Future pregnancy prognosis good

Critical Points

  • Always send tissue for histology
  • Monitor hCG meticulously
  • hCG >20,000 IU/L at 1 month needs chemotherapy
  • High cure rates with proper management

Molar Pregnancies & Gestational Trophoblastic Disease

Abnormal conceptions with excessive placental development requiring specialized management

Overview

Gestational trophoblastic disease (GTD) comprises a group of disorders spanning the premalignant conditions of complete and partial molar pregnancies (also known as hydatidiform moles) through to the malignant conditions of invasive mole, choriocarcinoma and the very rare placental site trophoblastic tumour (PSTT) and epithelioid trophoblastic tumour (ETT).

Hydatidiform moles are abnormal conceptions with excessive placental, and little or no fetal, development. The two major types—complete and partial—have distinctive histological and genetic features.

Epidemiology

Incidence

  • 1-3 in every 1000 pregnancies
  • 10% transform into malignant GTN
  • Higher risk in Asia and Latin America

Risk Factors

  • Age extremes: Under 16 (6x higher risk) and over 50 (1 in 3 chance)
  • Previous molar pregnancy
  • Dietary deficiencies (carotene, animal fat)
  • Blood group A women with group O partners

Types of Molar Pregnancies

Complete Hydatidiform Mole

  • Genetics: 46,XX (paternal origin only)
  • Fetal tissue: Absent
  • Villi: Diffuse hydropic swelling
  • Trophoblast: Diffuse hyperplasia
  • hCG levels: Very high
  • Malignant potential: 15-20%

Partial Hydatidiform Mole

  • Genetics: 69,XXX or 69,XXY (triploid)
  • Fetal tissue: Present but abnormal
  • Villi: Focal hydropic changes
  • Trophoblast: Focal hyperplasia
  • hCG levels: Moderately elevated
  • Malignant potential: 1-5%

Malignant Forms (GTN)

Type Features Incidence
Invasive Mole Penetrates myometrium, may metastasize 15% of complete moles
Choriocarcinoma Malignant epithelial tumor, high metastasis risk 2-5% of complete moles
PSTT/ETT Very rare, intermediate malignancy <1%

Clinical Features

Common Presentation

  • Irregular vaginal bleeding (most common)
  • Positive pregnancy test
  • Supporting ultrasonographic evidence
  • Uterus larger than dates (50%)
  • Hyperemesis gravidarum (20-30%)

Less Common Presentations

  • Excessive uterine enlargement
  • Hyperthyroidism (7%) due to hCG cross-reactivity
  • Early-onset pre-eclampsia (before 20 weeks)
  • Abdominal distension due to theca lutein cysts
  • Respiratory symptoms (trophoblastic embolization)

Rare Advanced Presentations

  • Haemoptysis (lung metastases)
  • Seizures (CNS metastases)
  • Vaginal metastases
  • GI bleeding (liver metastases)

Diagnosis

Ultrasound Findings

Complete Mole

  • 5-7 weeks: Polypoid mass
  • After 8 weeks: "Snowstorm" or "cluster of grapes" appearance
  • No identifiable gestational sac
  • No fetal parts
  • Bilateral theca lutein cysts (25-50%)

Partial Mole

  • Enlarged placenta with cystic changes
  • Fetal parts may be visible but abnormal
  • May present as delayed miscarriage
  • Cystic changes within decidual reaction

Histological Diagnosis

Critical: Because the diagnosis of hydatidiform mole is often unsuspected until histological examination, all products of conception from non-viable pregnancies must be submitted for routine pathological evaluation.

Feature Complete Mole Partial Mole
Fetal tissue Absent Present (abnormal)
Villi hydropic change Extensive, diffuse Focal
Trophoblast proliferation Excessive, diffuse Focal, mild to moderate
Scalloping of villi Absent Present
Trophoblastic inclusions Absent Present

Management

Molar Pregnancy Evacuation

Complete Moles

  • Suction curettage is the method of choice
  • Ultrasound guidance recommended
  • Minimizes perforation risk
  • Ensures complete tissue removal
  • Oxytocin infusion after cervical dilation

Partial Moles

  • Suction curettage preferred
  • Medical evacuation if fetal parts too large
  • Similar precautions as complete moles

Important Considerations

  • Anti-D prophylaxis recommended in Rh-negative women
  • Avoid hysterotomy if possible (increases metastasis risk)
  • Hysterectomy option for older women not desiring fertility
  • Chest X-ray recommended post-evacuation

Gestational Trophoblastic Neoplasia (GTN)

Women with hCG concentrations >20,000 IU/L one month after molar evacuation are at risk of uterine perforation and require chemotherapy to preserve fertility.

Chemotherapy Indications

  • hCG plateau for 3 consecutive weeks
  • hCG rise for 2 consecutive weeks
  • Histological diagnosis of choriocarcinoma
  • Metastatic disease present
  • hCG >20,000 IU/L 4 weeks post-evacuation

Treatment Protocols

  • Low-risk GTN: Single-agent methotrexate
  • High-risk GTN: Multi-agent chemotherapy (EMA-CO)
  • Response monitored by serial hCG measurements
  • Treatment continues until hCG normal for 6-8 weeks

Follow-up and Prognosis

hCG Monitoring Protocol

Standard Follow-up Schedule
  1. Weekly hCG until normal for 3 consecutive weeks
  2. Monthly hCG for 6 months (complete mole) or 6-12 months
  3. More prolonged follow-up for high-risk cases

Contraception and Future Pregnancies

  • Avoid pregnancy during hCG monitoring period
  • Combined oral contraceptives safe once hCG normal
  • Future pregnancy risk of molar pregnancy: 1-2%
  • Early ultrasound recommended in subsequent pregnancies
  • Overall excellent prognosis for future fertility

Prognosis

Condition Cure Rate Comments
Non-metastatic GTN 100% With proper chemotherapy
Low-risk metastatic GTN 90-95% Good response to single-agent therapy
High-risk metastatic GTN 80-85% Requires multi-agent chemotherapy