AKT · Obstetrics & gynaecology/Early pregnancy

Molar pregnancy (GTD)

Gestational trophoblastic disease — abnormal conception

Overview

Gestational trophoblastic disease: abnormal proliferation of trophoblast. Complete mole (empty egg + paternal DNA, 46XX, no fetus) or partial mole (triploid, some fetal parts). Presents with bleeding, a large-for-dates uterus and very high βhCG; needs hCG surveillance for malignant transformation (choriocarcinoma).

Recognise

Early pregnancy bleeding (may pass "grape-like" vesicles), often a large-for-dates uterus
VERY high βhCG → exaggerated pregnancy symptoms: severe hyperemesis, early pre-eclampsia, hyperthyroidism (hCG mimics TSH)
USS: "snowstorm"/"cluster of grapes" appearance, no fetal heartbeat (complete mole)

Red flags

Choriocarcinoma (malignant GTD), thyroid storm, early/severe pre-eclampsia before 20 weeks

Differentials & how to tell them apart

MiscarriageβhCG falling/appropriate; no snowstorm; products are recognisable

Multiple pregnancyhigh hCG and large-for-dates but multiple fetuses on USS, no snowstorm

Hyperemesis gravidarummolar pregnancy is a CAUSE of severe hyperemesis (very high hCG) — exclude it with USS

Ectopic pregnancyempty uterus + adnexal mass, lower hCG

Investigations

βhCG markedly raised (often >100,000). Transvaginal USS (snowstorm/cluster of grapes). Definitive: histology of products after evacuation. TFTs (hyperthyroidism).

Management

Suction curettage + hCG surveillance (refer to trophoblastic centre)

1Suction curettage (evacuation) of the uterus; send tissue for histology; register with a trophoblastic screening centre.Gate: Monitor serial βhCG to normalisation and AVOID pregnancy until hCG normal → a new pregnancy masks malignant transformation
2Persistent/rising hCG (gestational trophoblastic neoplasia) or choriocarcinoma → chemotherapy (methotrexate first-line for low-risk).

Suction curettage (evacuation) — remove molar tissue

Methotrexate / chemotherapy — for gestational trophoblastic neoplasia / choriocarcinoma

Anti-D — rhesus-negative (partial mole; complete moles have no fetal RhD)

Key points

Very high hCG drives the exam clues: severe hyperemesis, pre-eclampsia BEFORE 20 weeks, and biochemical hyperthyroidism (hCG cross-reacts at the TSH receptor). hCG surveillance is the management theme; choriocarcinoma can follow.

Monitor & prognosis

Serial βhCG to normal then for months; contraception (avoid pregnancy) during surveillance.

Excellent; choriocarcinoma is highly chemo-sensitive.

Source: RCOG Green-top 38 (GTD); QuackQuackMed cross-check