Molar Pregnancy

What is the clinical setting when you will consider molar pregnancy?

• Possible modes of presentation include:
  • Continuous or intermittent bloody discharge by about 12 weeks, not copious, and often more brown than red.
  • Uterine enlargement out of proportion to the duration of pregnancy in about 50% of cases.
  • No fetal parts or fetal heart sounds even though the uterus may be enlarged to a level at or above the umbilicus.
• Serum hCG level higher than expected for the stage of gestation.
• Preeclampsia/Eclampsia before 24 weeks (Pathognomonic).
• Hyperemesis gravidarum.
• Thyrotoxicosis.
• Embolization: amounts of trophoblast can escape into venous outflow at evacuation producing s/s of pulmonary embolism.
• Hydatid vesicles that resemble grapes can be passed before the mole is aborted spontaneously or removed by surgically. 
• Spontaneous expulsion is usually at 16 weeks and is rare beyond 28 weeks.  

What is the useful imaging modalities to evaluate molar pregnancy? What is the utility of the procedure, including limitations and accuracy?  

• The greatest diagnostic accuracy for molar pregnancy is obtained from the characteristic ultrasound appearance of hydatidiform mole.
• The combined use of sonography and serum beta-hCG determination appears to improve diagnostic accuracy for molar pregnancy. 
• Occasionally, other structures may appear similar to a mole on ultrasound, including intrauterine myoma and pregnancies with multiple fetuses. 
• The classic appearance of complete moles on ultrasonography is seen in less than two thirds of cases and even less commonly in the first trimester. 
• The prevalence of theca lutein cysts is very low.                

What are the imaging findings of molar pregnancy?

Complete hydatiform mole (CHM): Uterine cavity filled with multiple sonoluscent areas of varying size and shape, "snowstorm pattern." No embryonic or fetal structure. No amniotic fluid Theca lutein cysts (bilateral, multilocular ovarian cysts > 6 cm in diameter) It is possible to have a twin/triplet CHM with a normal fetus in a normal placenta coexisting with the CHM.

Parteial hydatiform mole (PHM): Enlarged placenta containing multi cystic, avascular, sonoluscent spaces, "swiss cheese" appearance. Fetal or embryonic tissue is present, may be viable, and is often growth restricted Amniotic fluid is present but reduced.  Increased transverse diameter of gestational sac. Theca lutien cysts are absent. Diploid/triploid mosaics and twin PHMs are also possible with a normal fetus along with the PHM within the enlarged placenta.