Belo Horizonte, Brazil

A 24-year-old woman presented with primary infertility, came to our office to make a first ultrasound, for dating. Vaginal sonography revealed an embryo with a single Y-shape trunk, two heads, two spines, one heart, and two arms. We did not see the legs. We thought that the embryo had caudal reduction.

Other things to consider in this case:

• Continuous skin contours at the same anatomic level, with skin edema.
• Absence of an inter amniotic membrane between the twins.
• Inability to separate fetal bodies.
• The heads and bodies of both twins are seen at the same level.
• Unusual extension of the spines (in this case we saw two spines).
• Permanent position of the fetus relative one to another, even after external stimulation or maternal movement.
• Single heart at thoracic transversal plane, seen in M-mode.