A 28-year-old woman was diagnosed by transvaginal ultrasound at 9+6 weeks with early fetal cardiac failure (hydrothorax and bradycardia). Doppler analysis of ductus venosus showed a negative A-wave pattern. The follow-up sonogram obtained at 11+6 weeks documented a missed abortion. A transvaginal ultrasound-guided coelocentesis was performed under local cervical anesthesia before uterine suction and 8 mL of clear extracoelomic fluid were successfully aspirated. Cytogenetic analysis demonstrated a 45,X karyotype. Ultrasound and Doppler waveform analysis of ductus venosus allowed early diagnosis of fetal cardiac failure. Coelocentesis may be the method of choice for early fetal karyotyping and may be used in the future to induce immunologic tolerance.