Movie 3.

Post-embolization, a hypoechogenic black mass can be observed moving inside the left atrium horizontally, in between the white arrows, confirming that the embolization was positive and that the embolus was limited to the left atrium. In this imaging plane, vessels arising from the vitelline circulation (encircled) can also be observed as moving bright white speckles (moving blood). These vessels should be avoided during needle advancement (by translating the needle out of the imaging plane) in order to prevent fetal demise.