Clinical signs and symptoms such as abdominal pain, cramps of the lower abdomen and vaginal bleeding during pregnancy are non specific. The uterus is often large for gestational age, and fetal heart beat is usually absent.
It is characterised 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; 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-retarded 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 blighted ovum, is notably absent
CT and/or MRI evaluation are not usually performed initially but may be used to determine if there is extension of molar tissue outside the uterus. CT may show an enlarged uterus with areas of low attenuation, or hypoattenuating foci surrounded by highly enhanced areas in the myometrium.
Considerations on early ultrasound scans include:
- fetal demise with placental hydropic change: beta HCG levels are invariably low in this case
- twin pregnancy with one normal twin and one complete hydatidiform mole: the normal twin usually has its own normal placenta
- placental mesenchymal dysplasia
- 1. Naumoff P, Szulman AE, Weinstein B et-al. Ultrasonography of partial hydatidiform mole. Radiology. 1981;140 (2): 467-70. Radiology (abstract) - Pubmed citation
- 2. Fine C, Bundy AL, Berkowitz RS et-al. Sonographic diagnosis of partial hydatidiform mole. Obstet Gynecol. 1989;73 (3 Pt 1): 414-8. - Pubmed citation
- 3. Woo JS, Wong LC, Hsu C et-al. Sonographic appearances of the partial hydatidiform mole. J Ultrasound Med. 1983;2 (6): 261-4. J Ultrasound Med (abstract) - Pubmed citation
- 4. Woo JS, Hsu C, Fung LL et-al. Partial hydatidiform mole: ultrasonographic features. Aust N Z J Obstet Gynaecol. 1983;23 (2): 103-7. - Pubmed citation
- 5. Wladimiroff JW, Eik-Nes S. Ultrasound in obstetrics and gynaecology. Elsevier Science Health Science div. (2009) ISBN:0444518290. Read it at Google Books - Find it at Amazon
- 6. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. Thieme Medical Publishers. (2005) ISBN:1588901475. Read it at Google Books - Find it at Amazon
- 7. Nyberg DA, McGahan JP, Pretorius DH. Diagnostic imaging of fetal anomalies. Lippincott Williams & Wilkins. (2003) ISBN:0781732115. Read it at Google Books - Find it at Amazon