A 19-year-old woman presents at 16 weeks with uterus size large for dates, hyperemesis gravidarum, and vaginal bleeding. Ultrasound shows a 'snowstorm' appearance without a fetal pole. β-hCG is 450,000 mIU/mL. Which of the following karyotypes is MOST likely for a complete hydatidiform mole?
- A 69,XXY (triploid)
- B 46,XX (diploid, androgenetic) ✓
- C 46,XY (diploid, biparental)
- D 45,X (monosomy)
Correct answer: B. 46,XX (diploid, androgenetic)
Explanation
A complete hydatidiform mole is most commonly 46,XX and is entirely androgenetic in origin—formed when an empty egg (enucleate ovum) is fertilized by a sperm that then duplicates its chromosomes (dispermy is the second mechanism). There is no fetal tissue, no amniotic membranes, and diffuse trophoblastic proliferation. A partial (incomplete) mole is typically triploid (69,XXY or 69,XXX) resulting from fertilization of a normal ovum by two sperm, and may contain fetal tissue.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.