Complete hydatidiform mole

Complete hydatidiform mole (CHM) is a type of molar pregnancy and falls at the benign end of the spectrum of gestational trophoblastic disease

CHM is the commonest type of gestational trophoblastic disease.

Complete moles are characterized by the absence of a fetus or fetal parts (i.e. no embryonic tissues). There is a non-invasive, diffuse swelling of chorionic villi.

Approximately 90% of complete hydatidiform moles have a 46XX diploid chromosomal pattern with ~10% having a 46XY composition. All the chromosomes are derived from the sperm, suggesting fertilisation of a single egg that has lost its chromosomes.

Serum beta HCG levels are markedly elevated, out of proportion to the pregnancy. 

  • enlarged uterus
  • may be seen as an intrauterine mass with cystic spaces without any associated fetal parts
  • may be difficult to diagnose in the first trimester 6
    • may appear similar to a normal pregnancy or as an empty gestational sac
    • <50% are diagnosed in the first trimester
  • bilateral theca lutein cysts may also be seen on ultrasound
  • color Doppler interrogation may show high velocity with a low impedance flow

CT evaluation is not usually performed give its low resolution for the uterine assessment. CT may show an enlarged uterus with areas of low attenuation, or hypoattenuating foci surrounded by highly enhanced areas in the myometrium.

MRI may demonstrate a heterogeneous mass with cystic spaces distending the uterine cavity. Fetal parts are notably absent. Uterine zonal anatomy is often distorted although a hypoechoic irregular myometrial boundary may be seen 3.

  • T1: there may be areas of high signal corresponding to foci of hemorrhage
  • T2: there is heterogeneous high signal from the cystic spaces
  • T1 C+ (Gd): often demonstrates intense enhancement due to hypervascularity

MRI may also demonstrate bilateral theca lutein cysts.

Suction and curettage are used for evacuation are usually the routine treatment. Serial beta-hCG levels should be obtained until it reaches zero, as it is the main indicator of residual disease.

A complete mole is itself benign but is considered a pre-malignant lesion. Degeneration into more invasive and malignant types of gestational trophoblastic disease can occur in ~10-20% of cases.

Share article

Article information

rID: 14748
System: Obstetrics
Synonyms or Alternate Spellings:
  • Complete mole
  • Complete molar pregnancy
  • Complete hydatidiform mole (CHM)
  • CHM
  • Classic hydatidiform mole

Support Radiopaedia and see fewer ads

Cases and figures

  • Heterogeneously e...
    Case 1 - Complete hydatidiform mole on CT
    Drag here to reorder.
  • Case 2: Bunch of grapes sign
    Drag here to reorder.
  • Transabdominal ul...
    Case 3
    Drag here to reorder.
  • Case 4: on ultrasound
    Drag here to reorder.
  • Case 5: Complete hydatidiform mole with bilateral theca lutein cysts
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.