Partial hydatidiform mole

Last revised by Rohit Sharma on 20 May 2024

Partial hydatidiform mole is a type of molar pregnancy, which in turn falls under the spectrum of gestational trophoblastic disease

Clinical signs and symptoms such as abdominal pain, cramps of the lower abdomen and vaginal bleeding during pregnancy are common but non-specific. The uterus is often large for gestational age, and fetal heart beat is usually absent. 

It is characterized by its focal distribution, slower transformation, the presence of an embryo or fetus, and a triploid karyotype (70% are 69 XXY, 27% are 69 XXX, and 3% are 69 XYY). The extra set of chromosomes are often of paternal origin 7.

Definitive diagnosis by ultrasound is often difficult. Described sonographic features include 1,3:

  • greatly enlarged placenta relative to the size of the uterine cavity

  • cystic spaces within the placenta ("molar placenta"), which may not always be present

  • an amniotic cavity (gestational sac), either empty or containing amorphous inappropriately small fetal echoes which may be surrounded by a relatively thick rim of placental echoes with intermingling cystic spaces

  • presence of a well-formed but growth-restricted fetus, either dead or alive with hydropic degeneration of fetal parts being frequently present

  • some partial moles can have sonographic appearances indistinguishable from those of the common complete moles or missed abortions 3, although an echogenic rim around the sac, as found in missed abortion or anembryonic pregnancy, is notably absent

  • color Doppler interrogation may show high velocity and low impedance flow

CT evaluation is not usually performed given 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 can be used to determine if there is an extension of molar tissue outside the uterus. 

When a partial mole is suspected and there is a live fetus, counseling and genetic tests looking for triploidy should be offered (chorionic villus sampling or amniocentesis). 

Suction and curettage are used for evacuation.

Considerations on early ultrasound scans include:

ADVERTISEMENT: Supporters see fewer/no ads

Updating… Please wait.

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

 Thank you for updating your details.