Complete chorioamniotic separation and persistence of a yolk sac associated with triploidy.

Triploidy is a highly lethal condition, and is thus very rarely observed in live births. It may result in significant medical risk to the pregnant woman. A 32-year-old multigravid woman presented for prenatal care. Ultrasound examination at 14+3 weeks of gestation revealed a viable fetus with appropriate fetal biometry, but with evidence of chorioamniotic separation (CAS) and persistence of the yolk sac. Two weeks later, repeat ultrasound showed a large multicystic placenta and early fetal symmetrical growth restriction with persistence of CAS and yolk sac, raising the suspicion of fetal aneuploidy. Amniocentesis showed a fetal karyotype of 69,XXX. The histology of the placental tissue was a partial hydatidiform mole. Persistence of chorioamniotic separation and yolk sac during the early second trimester cannot be considered a reassuring finding. In such cases, fetal karyotyping should be considered, especially when an additional abnormality is found.